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Car Forum / GMC Cars / May 2005Quadrajet stumble... Any suggestions??
I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when giving it too much throttle (maybe last 1/3 of pedal travel) the engine falls flat on it's face. Acts like it would if it were not getting enough accelerator pump shot if you floor from a stop or low speed. Even out on the road doing 40-50 MPH it will still stumble and fall flat on it's face. Holding WOT it will kinda pick up a little and then die a bit and slowly pick up some more. It will still stumble even if you gradually roll into the throttle, slowly giving it more until it stumbles. I was wondering if those huge secondaries are flopping open too quickly and at too low of an RPM and giving an awful lean condition. I've never worked with a Quadrajet before so I don't know much about them. I've only used and rebuild Autolites and Holleys. I've downloaded some very detailed Quadrajet service manuals and am thinking I'll pick up a kit and rebuild it. I'm a little nervous about it as it seems like such a complex carb. In any case, if anyone has any ideas about that stumble/bog I'd appreciate it. Thanks. Cory > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 16 lines] > > Cory Check the vacuum advance and centrifugal advance. Sometimes the weights get dirty or rusty and won't move. H Yes Hairy is right, but in 86 that distributor probably has that crap EST system with no weights or springs. The timing is advanced by the ECM and the module in the base of the distributor. Also, does it have a mixture control solenoid on the top front of the carb? If so, it could be stuck lean which would cause a problem very similar to the one you describe. Also check fuel pressure and volume, along with float level. Biggest problem ever with Q-jets is when people rebuild them they over-tighten the bolts and screws in the top plate and warp the plate and main body. > > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 25 lines] > dirty or rusty and won't move. > H I didn't see any vacuum advance unit and there were a few wires coming out of the distributor so it may very well be one of those POS distributors. Not good for performance or mileage from teh sounds of it. On the top front passenger side of the carb there is an electrical plug going into the carb. IIRC there is also one other wire plugged into it on the other side, and then of course the electric choke wire. I have no idea why there would be wires going into a carburetor, so I'm kinda confused about that. Is that the mixture solenoid you mention? Can I get rid of that and bypass it to work like a normal carb? Shouldn't the mixture in a Quadrajet be controlled by the idle screws, the jets, and the stages of the metering rod?? Cory > Yes Hairy is right, but in 86 that distributor probably has that crap EST > system with no weights or springs. [quoted text clipped - 42 lines] > > dirty or rusty and won't move. > > H accelerator pump is not working properly > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 16 lines] > > Cory If you had read my original post you would know it's not an accelerator pump issue. The problem occurs when at high RPM in first gear and mashing the throttle, and even at high RPM in 1st gear and gently giving it more throttle. Accelerator pump plays no meaningful role under those conditions. Unless the secondaries on a Quadrajet are designed to flop right open instantly and there is an accelerator pump on the secondary side there should be no problem with the accelerator pump, as the one on the primary side is doing it's job nicely. The car will actually take off reasonably quick from a dead stop if you mash it, just don't mash it too far. I've also driven 300 miles straight with no accelerator pump, 75 of those miles were stop and go traffic (frustrating to no end!). I know what an accelerator pump issue feels like and how the engine will act without one. I also know how to drive a car with no accelerator pump. This is not an accelerator pump issue I'm having, it's definitely something else. I think it is in the carb but others have mentioned it may be a timing issue, so I may check that today and see if the distributor is advancing the timing as it should. I have a feeling the secondaries are flopping open too qucikly though, so I may try tying them closed and going for a test drive. I welcome any input, but please, read my post and think a little before posting something that makes no sense and you haven't even used simple grammer such as capitalization and periods. Going by a name like "I'm Right" I figgure you may just be a troll, so maybe I've wasted a minute or two of my time here. Oh well. Cory > accelerator pump is not working properly > [quoted text clipped - 23 lines] > > > > Cory >> > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is > when >> > giving it too much throttle (maybe last 1/3 of pedal travel) the engine >> > falls flat on it's face. Acts like it would if it were not getting > enough >> > accelerator pump shot if you floor from a stop or low speed. There is a spring that sets the tension on the flapper door above the secondary throttle plates. It's loose. Just look at it and stick your finger in the carb and move the plate and you'll see what I'm talking about. It's a very common problem. There is a "wind up" screw and a "lock screw." Turn the wind up screw until the plate just touches the body, then the specified amount more. Usually between 1/2 and one full turn, look in a service manual. Then tighten the lock screw. Al > >> > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is > > when [quoted text clipped - 12 lines] > > Al Thanks, that's goes along the lines of waht it felt like was happening. The darned thing acts like it wants to stall, then will kinda jerkily get the revs back up and smooth out a little. I'll check that spring and see how the flapper and mechanicsm looks to be set up. Hopefully that's the problem. > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 16 lines] > > Cory 1. Accelerator pump bad or linkage out of adjust. 2. Ignition Timing (most likely retarded too much) 3. Vaccum leak. Usually at base of carb. 4. Secondary jets too big. 5. Mixture screws adjusted wrong. Get a rebuild kit and CAREFULLY rebuild the unit. Yes it IS a complex unit and you have to watch out for little ball bearings falling out of passages (check valves) when you disassemble. They will fit in many places, but there is only one correct place :) Not sure if this unit has them, but be careful. Get an egg carton to save parts in. Take pictures with a digital camera so you know how to put it back together. Understand many rebuild kits are generic, so take the instructions with that in mind. If you can get a specific kit, buy that one and make sure you get the advanced kit as the tune up kits usually only contain float, needle seat and valve with minimul gaskets. You want a complete teardown kit. In my day I have rebuilt a number of carbs and while it is not rocket science you MUST document how you took it apart, get the float level correct and use correct torque on all bolts to prevent cracking or warpage. Take your time, follow the instructions and it will work like a charm. These beast are actually pretty forgiving and you have to screw up bad for it to not work at all. Of course if you want the best performance you must adjust it to spec. good luck Spaldeen > > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 51 lines] > > Spaldeen Thanks for the tips. I'll probably rebuild it one of these days. It looks like fuel may be seeping through one of the side gaskets or something, as looked a bit damp. I can do Autolites and Holleys in my sleep, by the Quadrajet does make me a little nervous. Looks like a lot of parts packed in tightly. I will do as you say and take pictures along the way, and get a complete rebuild kit. Cory > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 16 lines] > > Cory 86' has the "lovely" electronic Q-Jet. It has a primary mixture control solenoid and TPS sensor inside as well as an idle control motor connected to the computer. If the mixture control solenoid is sticking it can act this way. Also it sounds like the secondary metering rods/jets are dirty, causing it to lean out. I would run a can of cleaner through it, then spray the interior down good. Then see how it acts. These carbs are not real hard to work on BUT there are a few parts you have to watch out for. Mainly the TPS plunger under the air horn and the MCS connector. > > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is > when [quoted text clipped - 38 lines] > you have to watch out for. Mainly the TPS plunger under the air horn and > the MCS connector. What role does the computer play on this model of engine and car? I believe it controls the timing, is that it? What would it take to get rid of the computer, a new carb and distributor? Just thinking what to do should this computer stuff become a big annoying problem. In any case, what role does the mixture control solenoid play? Is this in place of a normal metering rod and jet? Or does it control the position of the metering rod instead of manifold vacuum? How do I test it to see if it is worknig correctly? Also, waht is an MCS connector?? Thanks for the help! Cory > > > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is > > when [quoted text clipped - 54 lines] > > Cory Mixture Control Solenoid = MCS connection. The computer controls that carb almost the same way it does a throttle body injection system. It uses the TPS (Throttle Position Sensor) to see where you have the pedal and then looks at the engine RPMs and Timing to see how many pulses it should hold the solenoid open to give the correct fuel mix for that throttle position. As the TPS moves it tells the computer to either richen the mix (pulses are held on longer) or lean it out (pulses are shut off sooner) Then it looks at the O2 sensor in the exhaust and sees if the mix is correct based on the voltage it is seeing there. The Idle control does almost the same thing but it controls airflow not fuel. The MCS controls the primary metering rods in place of the power piston that operates off vacuum. As for converting it isn't hard. You need an HEI distributor off an older small block, the ignition module for a 305, A Q-Jet off of an earlier non-computer car with a 305/307/350 small block (big blocks use higher flow metering and sometimes the large bore Q-Jet, you don't want it on a stock small block) . Remove the light bulb from the check engine light in the dash. Remove the wiring to the carb and tape it so it cannot short out (in case you ever wanted to convert it back) and remove the computer fuse (or remove the computer itself and store it) Bolt the carb on, bolt the dizzy in, set the timing. Start the engine and check the timing again. All bets are off if you live in any area that does smog testing since most of what you did during the conversion isn't allowed.. > Mixture Control Solenoid = MCS connection. > [quoted text clipped - 24 lines] > All bets are off if you live in any area that does smog testing since > most of what you did during the conversion isn't allowed.. Thanks for the detailed description. So the comptuer on this car really doesn't do much, huh? I don't see why a well tuned standard carb shouldn't be able to pass emissions. Heck, I'm sure I could get better mileage out of a normal carb and distributor, and better power too. Just takes a bit of tuning. Of course it's a learning experience with Chevy's, as personally the vast majority of my experience is with classic Fords (first car was a '67 Galaxie, now my daily drifver is a '68 Galaxie). They do emissions checks here, but they don't check under the hood, just what comes out the exhaust. This is just a daily driver type car so I'd rather not get into that stuff just yet. Is there any way to adjust the timing, or am I stuck with what the stock curve is? I can adjust initial timing, right? From that will the computers curve always be the same? Will it increase total timnig when I increase initial timing? Sorry for so many questions, but I'm not used to working on anything newer than the early '70s. Cory > Thanks for the detailed description. So the comptuer on this car really > doesn't do much, huh? Nope, not much, just fuel delivery control, ignition timing, air pump switching and torque convertor lock up. Pretty much the same as model year 2005 vehicles. > I don't see why a well tuned standard carb shouldn't > be able to pass emissions. Because they couldn't control the fuel mixture precisely enough to satisfy the feed gasses to the catalytic convertor. > Heck, I'm sure I could get better mileage out of > a normal carb and distributor, and better power too. A correctly operating mid 80s 305 with feedback controls could easily achieve mid 20s MPG in a "B" body (full size), and probably slightly higher in a "G" body like the Monte Carlo. The HO 305 in a Monte Carlo SS performed quite well for what it was. > Just takes a bit of > tuning. Of course it's a learning experience with Chevy's, as personally the > vast majority of my experience is with classic Fords (first car was a '67 > Galaxie, now my daily drifver is a '68 Galaxie). You'd be best advised to learn how this system works before you go tearing into it. sh.t canning the electronics because it's too technical for you is amateurish at best. > They do emissions checks > here, but they don't check under the hood, just what comes out the exhaust. Things can always change in that regard, and either way, you'd still be violating federal law, creating increased pollution and likely contributing to even more draconian emissions laws, rules and regulations and added repair costs to your fellow citizens. > This is just a daily driver type car so I'd rather not get into that stuff > just yet. Is there any way to adjust the timing, or am I stuck with what the > stock curve is? I can adjust initial timing, right? You can adjust the base timing to your hearts content, but... > From that will the > computers curve always be the same? Will it increase total timnig when I > increase initial timing? Yes it will, but the system has a knock sensor, so as soon as any knock is heard by the sensor, the timing will be retarded. The GM engineers weren't stupid, there is little to be gained by adjusting to anything other than what's on the VECI label > Sorry for so many questions, but I'm not used to working on anything newer > than the early '70s. It all can be learned if you put forth the effort. That and a few special service tools can yield an engine that runs and performs as it should. > > I don't see why a well tuned standard carb shouldn't > > be able to pass emissions. > > Because they couldn't control the fuel mixture precisely enough > to satisfy the feed gasses to the catalytic convertor. Newsflash, catalytic converters have been used on non-electronically controlled carburetors. Perhaps "they" don't know how to tune a carb properly. > > Heck, I'm sure I could get better mileage out of > > a normal carb and distributor, and better power too. [quoted text clipped - 4 lines] > The HO 305 in a Monte Carlo SS performed quite well for what it > was. I've seen comparable mileage without electronic crap from various '60s cars. No electronics or feedback controls there. > > Just takes a bit of > > tuning. Of course it's a learning experience with Chevy's, as personally the [quoted text clipped - 4 lines] > go tearing into it. sh.t canning the electronics because it's > too technical for you is amateurish at best. If you had read my post without jumping to conclusions you would know that the reason for not wanting the electronics was the apparent inability to tune the timing and mixture. > > They do emissions checks > > here, but they don't check under the hood, just what comes out the exhaust. [quoted text clipped - 3 lines] > likely contributing to even more draconian emissions laws, rules > and regulations and added repair costs to your fellow citizens. Violating the federal law does not mean increased pollution. I know a guy who swapped the stock 302 in his fox body Mustang for a 408W and no electronic controls and he passes emissions, the thing puts out less than the stock 302 with emissions carb and distributor did, and as you may guess it's a hell of a lot faster too. So long as it's "clean" why should it matter how that is achieved?? > > This is just a daily driver type car so I'd rather not get into that stuff > > just yet. Is there any way to adjust the timing, or am I stuck with what the [quoted text clipped - 10 lines] > The GM engineers weren't stupid, there is little to be gained by > adjusting to anything other than what's on the VECI label Right... Timing is a compromise between emissions and mileage. I've found on many vehicles that adjusting the timing curve, amount of advance and type and amoutn of vacuum advance several more MPG can be had along with better performance. I don't like computers controlling my engine. I want to control it as I want to know exactly waht it's doing and when it's doing it. If I can tell the comptuer exactly what to do then maybe this computer controlled stuff isn't so bad. Unfortunately that probably involves expensive tools. > > Sorry for so many questions, but I'm not used to working on anything newer > > than the early '70s. > > It all can be learned if you put forth the effort. > That and a few special service tools can yield an engine that > runs and performs as it should. "As it should" is nice and dandy, but I want my engines to run better than they "should", as you use "as they should" in terms of exact factory specifications and tune. I want my cars to be running optimally for mileage and performance, and if necessary compromise a little performance for more mileage on the daily driver. Cory > > > I don't see why a well tuned standard carb shouldn't > > > be able to pass emissions. [quoted text clipped - 5 lines] > controlled carburetors. Perhaps "they" don't know how to tune a carb > properly. Yes, catalytic convertors have been used on non electronically controlled carburetors, but you'd have to search long and hard to find such a set up on a 5 liter engine that was able to meet the federal emissions regulations in 1986, and do so for the required 50,000 miles. Ford certainly didn't have anything, Chrysler either. > > > Heck, I'm sure I could get better mileage out of > > > a normal carb and distributor, and better power too. [quoted text clipped - 7 lines] > I've seen comparable mileage without electronic crap from various '60s cars. > No electronics or feedback controls there. Too bad the 60s aren't the 80s, no? Here's an idea; sh.t can the whole PCV system and replace it with a road draft tube. > > > Just takes a bit of > > > tuning. Of course it's a learning experience with Chevy's, as personally [quoted text clipped - 10 lines] > the reason for not wanting the electronics was the apparent inability to > tune the timing and mixture. No conclusion jumped to. Being as I've been repairing these exact systems on a daily basis since before you were ejected from your daddys nut sack, and training people to repair these systems from about the time you wore diapers, I can state precisely that there is no way in hell that -you- can make any adjustments that would be better or more optimal than what the on-board computer is capable of. > > > They do emissions checks > > > here, but they don't check under the hood, just what comes out the [quoted text clipped - 6 lines] > > Violating the federal law does not mean increased pollution. That may be, but the law doesn't look at it that way. Tampering is tampering, there is no "but officer." > I know a guy > who swapped the stock 302 in his fox body Mustang for a 408W and no > electronic controls and he passes emissions, the thing puts out less than > the stock 302 with emissions carb and distributor did, and as you may guess > it's a hell of a lot faster too. So long as it's "clean" why should it > matter how that is achieved?? Pardon me while I have trouble believing that this "guy" that you know has access to a full tilt federally certified IM test facility and that he went to the trouble to run the eleven day long test sequence to achieve an OEM type emissions certification. IOWs, no it doesn't. > > > This is just a daily driver type car so I'd rather not get into that > stuff [quoted text clipped - 17 lines] > and amoutn of vacuum advance several more MPG can be had along with better > performance. And that is exactly what the on-board computer is capable of doing, hundreds of times per minute. You can't even open and close the hood that fast, much less make an adjustment. > I don't like computers controlling my engine. So why did you buy one that does? > I want to control > it I want to fly the space shuttle. > as I want to know exactly waht it's doing and when it's doing it. So go to e-bay and buy a scanner. An OTC Monitor 2000 is perfectly capable of outputting every but of serial data in this system and they can probably be had for $20.00 > If I > can tell the comptuer exactly what to do then maybe this computer controlled > stuff isn't so bad. You're befuddled by the carburetor already, how in hell are you going to come up with the smarts to manipulate the programming? > Unfortunately that probably involves expensive tools. There is a Monitor 2000 on e-bay right now, 29.99 with zero bids, 4 days left to bid. As for re-programming, well, it's already set for optimum mixture and timing at wide open throttle, and it's already set for optimum mixture and timing to achieve maximum fuel economy during cruise, strangely, I find it hard to believe that someone who couldn't afford a set of tires a few months ago is going to improve on what is already there. > > > Sorry for so many questions, but I'm not used to working on anything > newer [quoted text clipped - 9 lines] > and performance, and if necessary compromise a little performance for more > mileage on the daily driver. Ah, I suppose those idiot engineers at GM hadn't thought of that. Thousands of lines of code and odds are it has more to do with Chicken McNuggets than it does "mileage and performance." ... >> I want to control it > >I want to fly the space shuttle. hey! me too. my 1986 chevy 307 used to stumble and stall and everything. after a lot of money at the garage and a lot of parts changed, it runs ok. nothing special. just ok. i'd have to rebuild the whole engine to make it run like new. what would be the point? the only reason i'm driving this barge is because i can't afford a newer car. like a '96 impala. ...thehick <snip> You're not even worth my time. All I have to say is that last post of yours shows just how truly pathetic you are. I pity you, and your immediate family. God bless them for putting up with you, assuming you have an immediate family that is. Cory > <snip> > [quoted text clipped - 4 lines] > > Cory If you don't want accurate information with which to solve your problem, what the f.ck are you doing here? You want to play a mechanic and fix your car? Great, do it right instead of sh.t canning everything and anything which you don't understand or are too lazy to learn to repair correctly. Or be scoffed at. Everything on that car of yours can be analyzed with a dwell meter and a digital multi-meter (so much for your expensive equipment beliefs) , you're just too stupid and lazy to do so, and as a result, the rest of us are supposed to gag on what comes out of the tailpipe and suffer tighter and stricter emissions testing requirements. Typical self centered adolescent. >> <snip> >> [quoted text clipped - 24 lines] > > Typical self centered adolescent. Very well said. Roy >I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when >giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 16 lines] > > Cory I had that once... turned out I put the fuel filter in backwards. Vuarra Quid quid latine dictum sit altum videtur. (That which is said in Latin sounds profound.) > I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 16 lines] > > Cory I got all the parts today. When I rebuild the carb is there a way to test the solenoid in the carb to ensure it is working correctly before I put it all back together? What range of resistance should the TPS have from idle to WOT? Anything else I need to know to ensure the carb is working properly? To se the timing on this engine do I have to unplug the distributor or short/jump any pins? Anything else I should know about this system? Thanks again to those with helpful input and advice! Cory > I got all the parts today. When I rebuild the carb is there a way to test > the solenoid in the carb to ensure it is working correctly before I put it > all back together? 12 volts applied to the solenoid connection, the MC plunger should pull down to its lean stop. > What range of resistance should the TPS have from idle to > WOT? Resistance is meaningless. The correct TPS adjustment is .52 volts at idle setting, it should go to near 5 volts at WOT (anything above 4.5 volts is acceptable). >Anything else I need to know to ensure the carb is working >properly? You'll need the lean stop measurement gauge to correctly set the metering rod travel and the double "D" sockets to remove / replace the MC solenoid and to adjust it (two sizes). Then there is a different double "D" socket for removing / replacing / adjusting the idle mixture screws, and a female hex socket for adjusting the TPS. <http://www.chevyasylum.com/tech/carbtool.html> mentions a few... Choke settings are best done with a "choke angle gauge." (you'll need a mity-vac or some other such vacuum source) > To se the timing on this engine do I have to unplug the distributor or > short/jump any pins? Timing set instructions are on the VECI label, but in general, Chevrolet carbureted engines were "disconnect the 4 wire connector" coming out of the distributor. > Anything else I should know about this system? > Thanks again to those with helpful input and advice! The MC solenoid duty cycle can be read with a dwell meter set to the 6 cylinder scale, the dwell meter is connected to the single "green" connector which breaks out of the electrical harness near the carburetor and a good ground. You'll want the dwell varying in between 25* and 35* at idle and at fast idle. > > I got all the parts today. When I rebuild the carb is there a way to test > > the solenoid in the carb to ensure it is working correctly before I put it [quoted text clipped - 39 lines] > the carburetor and a good ground. You'll want the dwell varying > in between 25* and 35* at idle and at fast idle. Thanks a lot for all the information. This is exactlyu the type of stuff I was asking for in the first place. Although I have a general idea how this stuff works I don't know all the ins and outs of it, and need to get that information from somewhere. Thanks again, you've been very helpful here. Aslo ,I think I figured out the MCS works properly... I did teh plugs,wires, cap and rotor earlier and the car ran poorly afterwards. It idled rough and smelled pig rich. When I drove it though it ran very strong once I opened the throttle a bit. Opened the hood again adn saw I forgot to reconnect the O2 sensor wire on the driver's side. Apparently since it wasn't getting a signal it defaulted to lean and tried to richen it up to compensate! This stuff is actually kinda cool. > In article <joednRFRmo3MVRXfRVn-1w@comcast.com>, I took the carb apart and cleaned it up pretty good. It made a world of difference. The car idles and runs much smoother now and it has more power. It still bogs when the secondaries come in, but I still have to get that adjusted right. Even at the same setting though it bogs a lot less and runs much nicer. I've never seen a carb with so much crud and nasty build-up inside it, not even old Autolites! Two questions... The tall screw holding the plate that holds down the MCS... How much do I tighten that or adjust that to? I set it so there is light tension on the spring below the screw. It seems to run alright like that, but I would like to know the correct setting. I counted the turns but I can't find the apper I wrote it down on (d'oh!). Also, how do I adjust the TV cable? Aftrer removing it I don't see how to tighten it. The cable just slides through the part that clips onto the throttle lever. I figure there must have been a clip on the end or something but can't find anything. Anyhow, how do I set it properly and how do I attach it to the throttle lever/clip? I don't wanna drive it much without getting that TV cable adjusted right. I know on Ford AOD's if it's way out of whack you can burn up the clutches in the transmission, so I don't wanna risk that. Cory TV cable is easy on most later vehicles. The cable end attaches to either a T stud on the throttle arm on the carb or uses a pin through a hole. Then you release the cable lock and pull the cable back through the lock. Get in the car and step on the gas. Go back under the hood and lock the cable back in place with the clip. http://www.tciauto.com/instructions/gm_tv_cable_adjust.htm for a quick look.  SignatureSteve Williams > > In article <joednRFRmo3MVRXfRVn-1w@comcast.com>, > [quoted text clipped - 22 lines] > > Cory I adjusted it as per that site. It helped, but there is still a problem... In overdrive the car 'shudders' a bit when you are lightly accelerating at a certain point of throttle opening. Give it a little more and it smooths out. Or put it in drive and there is no problem. What might this be?? Cory > TV cable is easy on most later vehicles. The cable end attaches to > either a T stud on the throttle arm on the carb or uses a pin through a [quoted text clipped - 45 lines] > > > > Cory Converter going in/out of lock sometimes causes a slight tremor. Might want to pull the pan and change the filter and fluid in the trans if you haven't done that yet. If the fluid is older it could be less lubricating than normal and may cause stiction in the converter clutch. There is a way to test that by disconnecting the converter clutch wiring and trying it , just don't run it a lot like that since it could burn up the clutches in the trans. I forget which connector it is on that car but a wiring diagram will show it. SignatureSteve Williams > I adjusted it as per that site. It helped, but there is still a problem... > In overdrive the car 'shudders' a bit when you are lightly accelerating at a [quoted text clipped - 13 lines] > > > > > "aarcuda69062" <nonelson@sbcglobal.net> wrote in message news:nonelson-7572CE.13570116052005@newsclstr01.news.prodigy.com... > > > > In article <joednRFRmo3MVRXfRVn-1w@comcast.com>, > > > [quoted text clipped - 36 lines] > > > > > > Cory > Two questions... The tall screw holding the plate that holds down the MCS... > How much do I tighten that or adjust that to? I set it so there is light > tension on the spring below the screw. It seems to run alright like that, > but I would like to know the correct setting. I counted the turns but I > can't find the apper I wrote it down on (d'oh!). That is the lean mixture stop adjustment. To properly set it, you need the special gauge that fits over one of the main jets, then the screw is adjusted so that when the metering rod plunger is pushed down, it -just- touches the gauge. (This is done without the metering rods installed in the jets.) Once set, the top is put on the carb and the total metering rod travel is set by adjusting the rich stop (the larger double "D") that screws into the carb top. Travel is measured by dropping the special float level gauge into one of the vent holes either side of the idle air bleed plunger at the front center of the air horn, correct metering rod travel is 3/32" - 4/32" lean to rich. The top end of the rich stop screw is hidden under an aluminum anti-tamper plug, to remove the plug the rich stop screw is removed from the carb top with the large double "D" socket, once out, a pin punch is used to drive the anti-tamper plug out of the carb top. This allows using the smaller double "D" socket to adjust the rich stop when the top is back on the carb. All anti-tamper plugs are then installed where they should be once the carb is back together and adjusted correctly. The anti-tamper plugs should not be left out since they hold the various screws they cover in place and keep them from moving. (exception being the two idle mixture screw plugs.) Lacking the correct lean gauge, bottom the screw gently, then back it out three turns, that should get you close. Lacking the correct float gauge, fashion your own from a wooden match stick or soda straw (or similar), by marking it in 1/32" intervals. I make the final adjustments with the carb installed and the engine running at a fast idle (1800 RPM or so), connect a dwell meter to the green lead that breaks out of the computer harness near the carburetor, high dwell means a lean mixture command, low dwell means a rich mixture command. If the dwell trends towards 50* adjust both the lean and rich MC solenoid stop screws -down- in 1/4 turn increments, if the dwell trends towards 10* adjust the MC solenoid stop screws -up- in 1/4 turn increments. The object is to get the dwell reading varying between 30 and 35 degrees. Same goes for idle mixture except that you're going to adjust the idle mixture screws and the idle air bleed valve at the front of the air horn. The original GM training course on this system was three days long, so you've got your work cut out for you... > Also, how do I adjust the TV cable? Aftrer removing it I don't see how to > tighten it. The cable just slides through the part that clips onto the > throttle lever. I figure there must have been a clip on the end or something > but can't find anything. Anyhow, how do I set it properly and how do I > attach it to the throttle lever/clip? The TV cable pulls out as the throttle is opened, it attaches on the lower side of the throttle lever (make sure you're putting it in the right place). The adjustment for the TV cable is where the cable casing bolts down to the manifold or carb, there is either a metal latch that you depress to release the cable casing, or a plastic latch that is lifted up to release the cable casing. Adjust so that when the throttle is at wide open, the TV cable is at its maximum extension. Honest to god truth, the TV cable rarely needs adjustment just because the carb has been removed. > I don't wanna drive it much without getting that TV cable adjusted right. I > know on Ford AOD's if it's way out of whack you can burn up the clutches in > the transmission, so I don't wanna risk that. Your caution is well warranted. > > Two questions... The tall screw holding the plate that holds down the MCS... > > How much do I tighten that or adjust that to? I set it so there is light [quoted text clipped - 45 lines] > The original GM training course on this system was three days > long, so you've got your work cut out for you... Okay, I got the TV cable adjusted and it works better now. There is one issue still though. In overdrive right around 34 MPH under light throttle the car will shudder a bit. Also on the highway sometimes under very light acceleration it will shudder a bit. Any thoughts? It feels like it may be the torque converter locking/unlocking real quick. Could it be I don't have the TV cable adjusted properly?? I read some stuff online that said how to set it and that was the same as how you said to. I will make the 3 turns base adjustment to the lean screw in the carb and check with my dwell meter. Where can I get a tool to adjust the idle mixture screws while the carb is on the engine? I didn't find any double D bits/sockets at Advance today when I went for wires/cap/rotor for the Galaxie. I want to learn these Quadrajets as I want to put an early one on the Galaxie for better mileage (14-15 MPG with the Holley isn't cutting it). It seems like the early non-computer Quadrajets should be a heck of a lot easier. They seem fairly similar to Edelbrocks in some respects. Cory > Okay, I got the TV cable adjusted and it works better now. There is one > issue still though. In overdrive right around 34 MPH under light throttle > the car will shudder a bit. Also on the highway sometimes under very light > acceleration it will shudder a bit. Any thoughts? It feels like it may be > the torque converter locking/unlocking real quick. Could it be I don't have > the TV cable adjusted properly?? The TPS (throttle position sensor) has authority over TCC lock up, it along with the VSS (vehicle speed sensor) are what determines TCC lock up as long as the various pressure switches in the transmission valve body are closed. If you get the same sensation by lightly touching (riding) the brake pedal and then letting off, it's the TCC engaging. If you've got a dash mounted tach, you'd see an RPM change when the TCC cycles on and off. The mid 80s Chevies didn't have very sophisticated control stategy, unlike newer stuff where the TCC is applied gradually via duty cycling the circuit... Best way to make sure the TCC is applying correctly is to make sure the TPS voltage is set at curb idle speed. .55 volts. > I read some stuff online that said how to > set it and that was the same as how you said to. I wouldn't lie to you... 8^) > I will make the 3 turns base adjustment to the lean screw in the carb and > check with my dwell meter. Where can I get a tool to adjust the idle mixture > screws while the carb is on the engine? I didn't find any double D > bits/sockets at Advance today when I went for wires/cap/rotor for the > Galaxie. Thexton: <http://www.thexton.com/vshop/shopexd.asp?id=194&catid=35> This is a flexible shaft tool for adjusting the idle mixture screws, I used one for many years. <http://www.thexton.com/vshop/shopexd.asp?id=197&catid=35> These are the sockets for servicing all the oddball adjustments on Rochester feedback carburetors. I still use 'em. <http://www.tooldiscounter.com/ItemDisplay.cfm?lookup=THE370&sourc e=froogle&kw=THE370> This kit has the lean stop gauge, the external float gauge which also works for measuring MC solenoid travel and the idle air bleed gauge. The lean stop gauge is not as nice as the OEM factory issued stuff but it should work fine, the other two tools look pretty close to OEM factory. I believe this set has been discontinued by Thexton, if these guys have it in stock, I'd grab it quick. <http://www.thexton.com/vshop/shopexd.asp?id=131&catid=36 > Choke angle gauge, only way to get the primary and secondary choke pull-offs and fast idle cam position set correctly. I used this one for a few years and then bought one from Snap-On for much more $$. It'll work fine for occasional use. > I want to learn these Quadrajets as I want to put an early one on the > Galaxie for better mileage (14-15 MPG with the Holley isn't cutting it). It > seems like the early non-computer Quadrajets should be a heck of a lot > easier. They seem fairly similar to Edelbrocks in some respects. This page has some useful info. <http://members.dandy.net/~k0xp/Oldsmobile/ElectronicQjetPix.htm> More stuff can be found at his index: <http://members.dandy.net/~k0xp/Oldsmobile/> Q-Jets and Dual Jets are excellent carburetors -when- set up correctly. > > Okay, I got the TV cable adjusted and it works better now. There is one > > issue still though. In overdrive right around 34 MPH under light throttle [quoted text clipped - 66 lines] > Q-Jets and Dual Jets are excellent carburetors -when- set up > correctly. Very true. When set up properly the Qjet can be a great mixer. Very tunable once you learn the tricks. Nice thing about them is you can set them up to give great throttle response and great WOT because of the different sized throttle bores. The main problem was the welch plugs under the bodies that leaked after a while, pull them clean them and epoxy and no more leaks. Put a good filter in them and install a heat shield to keep the carb body cooler. Possibly stack a couple base gaskets as well to reduce the heat more. Remember that on the front bores your running a 350-400 CFM carb (better mileage and throttle response) and when the rear bore tip in you go up to 750-850 CFM. Once you figure them out you can play head games with folks at the track. My favorite car to run was my older Nova with a BB 454 with twin Q-Jets mounted on a cross ram intake. Fun to drive around town with the smaller bores doing the work and REAL fun at the track when you stomped the loud pedal... > Once you figure them out you can play head games with folks at the > track. My favorite car to run was my older Nova with a BB 454 with twin > Q-Jets mounted on a cross ram intake. Fun to drive around town with the > smaller bores doing the work and REAL fun at the track when you stomped > the loud pedal... How did it run? Al 73 Nova, 454 powered:) > > Once you figure them out you can play head games with folks at the > > track. My favorite car to run was my older Nova with a BB 454 with twin [quoted text clipped - 5 lines] > > Al 73 Nova, 454 powered:) Mine was a 69. With a CrowerGlide in it I could get into the mid 10s on street rubber and pump gas. Gained another half with slicks and good fuel. Not bad for a street legal toy. I sold it to a guy who put a gas kit on it and set it up more like a real pro stock car. His second pass he lost it and went into the rails and destroyed the car. I have a 74 hatchback that I may play with some. Have a nice alloy block in the shop..... SignatureSteve Williams > I want to learn these Quadrajets as I want to put an early one on the > Galaxie for better mileage (14-15 MPG with the Holley isn't cutting it). [quoted text clipped - 3 lines] > > Cory Caution. Putting a Q-Jet on an adapter is asking for trouble if you use an adapter with an open center. The Q-Jet has a large screw right in the center. If it falls in the engine, KABOOM! Al > > I want to learn these Quadrajets as I want to put an early one on the > > Galaxie for better mileage (14-15 MPG with the Holley isn't cutting it). [quoted text clipped - 9 lines] > > Al Thanks for the warning. I plan on using a 4 hole adaptor and massaging it as needed to ensure good airflow thorugh it. Cory The early Quadrajet carburetors were prone to quick wear in the cast iron base where the throttle plate shafts passed through it. One end had the bellcrank for the linkages the other a clip retainer. Over time, as pressure was put on the bellcrank by the linkages to open the throttle plates, it caused the hole in the base to wear in an oval shape and this caused an idle mixture that fluctuated engine idle up and down and rpm's at other low throttle openings. Some manufactures came out with a "nylon sleeved repair kit." This consisted of two nylon bushings and a few brass washers. The process was to remove the screws holding the throttle plates in their slots in the throttle shaft and then removing the shaft itself. After that you drilled a larger hole as specified THROUGH the existing holes in the base, installed the throttle shaft back through these nylon bushings and washers and then reinstalled the throttle plates. All of this is to tell you to inspect the throttle shaft holes and the fit for looseness on ANY of these Quadrajets you plan on buying. Hope this helps. I'm a really old guy who had shops and rebuilt a few of these a long time ago when they were "new" technology. The technology has all pretty much passed me now and I am amazed most of the time at the knowledge and expertise of some of you younger fellows in this newsgroup. Bob... >> > I want to learn these Quadrajets as I want to put an early one on the >> > Galaxie for better mileage (14-15 MPG with the Holley isn't cutting [quoted text clipped - 17 lines] > > Cory >I just got an '86 Monte Carlo LS with a 305 and Quadrajet. Problem is when > giving it too much throttle (maybe last 1/3 of pedal travel) the engine [quoted text clipped - 21 lines] > > Cory Sounds like my 85 van. Timing and idle were way off. Numerous bad vaccum hoses. Loose carb screws and bolts. PCV system all clogged up. Replaced PCV valve adjusted idle set timming new vaccum lines .Runs nice. MPG went from 10 to 16 |
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