 |
 | Home | Contact Us | FAQ | Search & Site Map | Link to Us |
 | Sign In | Join | Other 45 Sites in Network |
Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / May 200581 Corvette - too rich for me
I bought an 81 Corvette a couple of years ago. It runs great BUT, it smokes black when it's idling and still smokes black a little when it's warmed up. I know it's not an economy car but it also gets pretty bad mileage. My guess is it's running really rich. I bought it in California near sea level and I live at 3700 ft. Could that change do it? I think it's a Quadrajet. How or what do I adjust? You think it's a Qjet ... sorry, I'm just one of the few that loves those things :-) ... if it was me I'd first check that the choke is fully open when the engine is warm ... if not there's work there; or maybe the float's allowing fuel to bypass; or if I was topping up the oil frequently a compression check (wet, dry) for valve, rings wear. Or could be the previous owner supersized :-) the jets ... a link ... http://www.tocmp.com/manuals/Carbs/Rochester/QJet/ > I bought an 81 Corvette a couple of years ago. It runs great BUT, it > smokes black when it's idling and still smokes black a little when it's > warmed up. I know it's not an economy car but it also gets pretty bad > mileage. My guess is it's running really rich. I bought it in > California near sea level and I live at 3700 ft. Could that change do > it? I think it's a Quadrajet. How or what do I adjust? I have had problems with the choke. It's electric and when I got the car I think the wrong wire was connnected to it so it never pulled off properly. But now I've got the right wire. I *think* it pulls back all the way, I had problems adjusting it to the right position, but even if it was still closed by 1/8 inch or so, would that make it smoke black? Compression check was fine and it doesn't use unusual amounts of oil. So except for the smoke, it runs well? I guess yer right ... it's just been set up to run rich. Now, someone once posted that if a catalytic converter were to be removed, there might be extra smoke ... maybe look into that and check out the cat(s)? > I have had problems with the choke. It's electric and when I got the > car I think the wrong wire was connnected to it so it never pulled off > properly. But now I've got the right wire. I *think* it pulls back all > the way, I had problems adjusting it to the right position, but even if > it was still closed by 1/8 inch or so, would that make it smoke black? > Compression check was fine and it doesn't use unusual amounts of oil. Catalytic converters are still there. I checked 'em when I put on a muffler last year. Although I did have question about whether removing them would give me a little more power. 81's aren't exactly power machines. Yes, having the choke plate slightly closed will make it blow black smoke. I recommend you get a manual for the vehicle. Even the cheap Haynes manual is pretty good for the older vehicles. It will give you the basics for setting the idle mix and choke anyway. It sounds like that might be a bit rich, but I would get the choke right first. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's > I have had problems with the choke. It's electric and when I got the > car I think the wrong wire was connnected to it so it never pulled off > properly. But now I've got the right wire. I *think* it pulls back all > the way, I had problems adjusting it to the right position, but even if > it was still closed by 1/8 inch or so, would that make it smoke black? > Compression check was fine and it doesn't use unusual amounts of oil. If I recall, when the choke was set so it fully closed, then it wouldn't fully open, and when we set it so it would fully open, it wouldn't fully close. But I don't recall any way to make it have a bigger range of operation. Haynes would be a good idea. If the choke is an electric bimetal one and has run out of range it is time to replace it or to make sure it has a strong 12V power signal. They are usually pretty cheap. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's > If I recall, when the choke was set so it fully closed, then it > wouldn't fully open, and when we set it so it would fully open, it > wouldn't fully close. But I don't recall any way to make it have a > bigger range of operation. > Haynes would be a good idea. What do you mean by 'strong' 12V power. Isn't 12 volts 12 volts? > I bought an 81 Corvette a couple of years ago. It runs great BUT, it > smokes black when it's idling and still smokes black a little when it's > warmed up. I know it's not an economy car but it also gets pretty bad > mileage. My guess is it's running really rich. I bought it in > California near sea level and I live at 3700 ft. Could that change do > it? I think it's a Quadrajet. How or what do I adjust? Sounds like it's time for a rebuild or a rebuilt. You might want to determine what kind of carb is on your car before doing much more. There should be a tag on the carb somewhere with info. It definitely says Rochester Quadrajet on the side. Couldn't see any other significant numbers because of the way it's stored. Is rebuilding pricey? > It definitely says Rochester Quadrajet on the side. Couldn't see any > other significant numbers because of the way it's stored. > Is rebuilding pricey? Rebuilt carbs are expensive: www.classicindustries.com/pdf/t03_fuel-exhuast.pdf I usually rebuild mine. This may be of help: http://www.corvettefever.com/howto/53360/ Last kit I bought was $65 US. In article <1114978614.474837.292820@z14g2000cwz.googlegroups.com>, > It definitely says Rochester Quadrajet on the side. Couldn't see any > other significant numbers because of the way it's stored. > Is rebuilding pricey? I'm surprised that no one has suggested checking for trouble codes. The diagnostic connector is under the ash tray, jumper pins "D" and "E" and count the check engine light flashes (you DO have a check engine light that comes on with the key, don't you?) Also; With pins D and E jumpered in the diagnostic connector, the mixture control solenoid in the carburetor should be clicking away at 10hz. Rich mixture can be caused by any number of things, such as; Sunk or misadjusted float Leaking needle and seat Choke not opening Coolant sensor error TPS error MAP sensor error Leaking welch plugs in the bottom of the carb main body Misadjusted mixture control solenoid adjustments No 12 volts to mixture solenoid Stuck or misrouted air pump valving No RPM signal to ECM from distributor Charcoal canister/evap/purge valve problems One can only wonder what all has been mangled, butchered and tampered with on this thing over the last 25 years Yes, I do have a check engine light that comes on. Never thought of doing the diagnostic check. Looks like I'm in over my head. I only know how to check about half of the things on your list :) Oh well, might be time to head to my friendly (just-leave-your-wallet-with-me) neighborhood mechanic. >I bought an 81 Corvette a couple of years ago. It runs great BUT, it > smokes black when it's idling and still smokes black a little when it's > warmed up. I know it's not an economy car but it also gets pretty bad > mileage. My guess is it's running really rich. I bought it in > California near sea level and I live at 3700 ft. Could that change do > it? I think it's a Quadrajet. How or what do I adjust? A very common problem with Quadrajets is the well plugs between the throttle plate and the bottom of the carb body will leak. Thexton makes a great kit that replaces the OEM well plugs with aluminum plugs with o-rings. Brian Don't know what well plugs are. Do you know of a diagram online? > Don't know what well plugs are. Do you know of a diagram online? Yep, right here. Brian http://www.stratagaz.com/Quadrajet/Quadrajet_7029202.htm Very helpful. Thanks. |
Reply to this Message |
 Sign In
 Join
 My Latest Posts My Monitored Threads My Blog My Photo Gallery My Profile My Homepage Start New Thread Enable EMail Alerts Rate this Thread
|
©2008 Advenet LLC Privacy Policy - Terms of Use
This website includes both content owned or controlled by Advenet as well as content owned or controlled by third parties.