 |
 | 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 / July 2006"Glowing" ex manifold on a 2.5L S-10
It's a 91 2.5L TBI ... the rig became progressively sluggish [over weeks] until it would hardly move. Any throttle movement would stall the engine. And the exhaust manifold was red hot before I chose not to drive it! Towed it home ... checked for a leaking TBI - NO CHANGE. Dropped the exhaust pipe - NO CHAGE. EGR's OK .. MAP appears OK related tubing and connectors OK ... where do I look next? Should I tear into the distributor? .. what should I look for? > It's a 91 2.5L TBI ... the rig became progressively sluggish [over > weeks] until it would hardly move. Any throttle movement would stall [quoted text clipped - 5 lines] > and connectors OK ... where do I look next? Should I tear into the > distributor? .. what should I look for? Check cam timing. I had an Olds v-8 that did the exact same thing. Turned out to be a very stretched timing chain.  SignatureSteve Walker fusion640@verizonwallet.net (remove wallet to reply) Steve ... No timing belt or chair ... gear to gear on this. It's possible I guess but I looking for something not quite that drastic. BUT you could be right?? > Check cam timing. I had an Olds v-8 that did the exact same thing. > Turned out to be a very stretched timing chain. > > -- > Steve Walker > fusion640@verizonwallet.net (remove wallet to reply) >It's a 91 2.5L TBI ... the rig became progressively sluggish [over >weeks] until it would hardly move. Any throttle movement would stall [quoted text clipped - 5 lines] >and connectors OK ... where do I look next? Should I tear into the >distributor? .. what should I look for? You have described perfectly the symptoms of grossly retarded ignition timing. Distributor is a likely culprit. Don www.donsaustomotive.com Don any suggestion on what to look for? I'll run through the factory fault tree ... but where should I look first? rotor, ESC module, etc.?? > You have described perfectly the symptoms of grossly retarded ignition > timing. Distributor is a likely culprit. > > Don > www.donsaustomotive.com > You have described perfectly the symptoms of grossly retarded ignition > timing. Distributor is a likely culprit. > > Don > www.donsaustomotive.com It does indeed. I have heard these exact symptoms before, and am trying to remember what was found. Seems that some of the issues were due to a loose wire or bad connection of some type, perhaps around the distributor area, but the details evade me at the moment. Don't know about this particular engine, but Ford Clevelands frequently break the distributor gear roll pin, which results in a severely retarded timing, if the engine doesn't stop completely. Had a friend suffer from this only two days ago, but as he was running a crank trigger he noticed that the engine started to sound funny at idle, and only after about 5 minutes did he notice that he had no oil pressure :-( We installed a new gear, with a proper press fit, and double pins. Apparently the engine is running fine. He has now installed an idiot lamp as well as an ignition kill switch which runs from an oil pressure switch. Don ... I'm going to check the wiring to the distributor from the ECM and look for anything unusual. One thing I failed to mention was that the engine begin to sound like there was a hole or crack in the header pipe. I expected to see a hole or sever crack somewere BUT I DIDN'T. That STILL baffels me. Could severely retarted timing cause detonation in such a way to cause this. > It does indeed. I have heard these exact symptoms before, and am trying to > remember what was found. [quoted text clipped - 3 lines] > the > moment. > It's a 91 2.5L TBI ... the rig became progressively sluggish [over > weeks] until it would hardly move. Any throttle movement would stall [quoted text clipped - 5 lines] > and connectors OK ... where do I look next? Should I tear into the > distributor? .. what should I look for? Sounds like it could be retarded timing like the other poster said. To me it sounds like first of all you are running real rich or are not burning fuel completely in combustion chamber. That is why exhaust manifold is cherry red , fuel is burning when coming out of exhaust port, either because rich mixture not burning completely or retarded timing would not burn all gas in chamber either. I would pull the sparkplugs and look at the tips, if real white insulator running lean, if a little brown or grey running good, if dry black insulator, running rich and could be shorting out spark, and if wet black could be oil control problem and also shorting out spark sometimes. Is there any black smoke coming out of tailpipe, then running rich, can you smell excessive gas smell after engine warmup (since engine will run rich if computer thinks it is cold through coolant temperature sensor) The good thing with TBI is you can remove air cleaner and look at fuel injectors squirting while engine running,(running without air cleaner OK for short periods of time), dont forget to plug any vacuum or exhaust lines to air cleaner. throttle body injectors have regulators that have low pressures that don't change since they squirt into atmosperic pressure unlike port fuel injectors. You could check fuel pressure anyway. You could check ignition timing also with a timing light and if way retarded could be timing belt or gear or chain problem, try adjusting ignition timing to see if run better than could be gear or chain or belt. I will try to check the timing, but I don't think I can get the engine to produce enough RPM ... it's idle is REALLY marginal. One thing I failed to mention was that the engine gradually began[over weeks] to sound like there was a hole or crack in the header pipe. I expected to see a hole or sever crack somewere BUT I DIDN'T. That STILL baffels me. Could severely retarted timing cause detonation in such a way to cause this. > Sounds like it could be retarded timing like the other poster > said. To me it sounds like first of all you are running real rich or [quoted text clipped - 20 lines] > problem, try adjusting ignition timing to see if run better than could > be gear or chain or belt. >I will try to check the timing, but I don't think I can get the engine >to produce enough RPM A very low idle is best for checking the timing. Put a timing light on it before you do anything else Don www.donsautomotive.com >... it's idle is REALLY marginal. > [quoted text clipped - 28 lines] >> problem, try adjusting ignition timing to see if run better than could >> be gear or chain or belt. >A very low idle is best for checking the timing. Put a timing light >on it before you do anything else For initial ignition timing, it must be done at "curb idle". That is, running, parked. At the proper RPM. No slower, no faster. It must be at factory specs. Idle speed should be as such. If you rev it up to 2000 RPM, it's still "idling", but that doesn't count. Adjust it to factory spec curb idle speed, then check initial ignition timing. Then, rev it up and check centrifugal advance. Signature-john wide-open at throttle dot info >>A very low idle is best for checking the timing. Put a timing light >>on it before you do anything else [quoted text clipped - 5 lines] >At the proper RPM. >No slower, If its slower than specified curb idle this will be only a small difference -- if any. Close enough to verify the problem and get the thing in the ballpark. Reved up is much worse -- could be off 20* or more. Don www.donsautomotive.com > no faster. >It must be at factory specs. [quoted text clipped - 7 lines] > >Then, rev it up and check centrifugal advance. The Randall43@gmail.com entity posted thusly: >I will try to check the timing, but I don't think I can get the engine >to produce enough RPM ... it's idle is REALLY marginal. [quoted text clipped - 4 lines] >STILL baffels me. Could severely retarted timing cause detonation in >such a way to cause this. Nobody has mentioned the possibility of some plugs not firing. I have a 2000 F-150 that had this problem on two cylinders, and while driving it to the dealership (about 30 miles away), i happened to look in the rear view mirror and saw bright sparks dropping onto the pavement and bouncing. It was chunks of something, superheated. Turns out that fuel was being sent unburnt into the exhaust system, burning there, and really messing things up. I don't know about you guys, but on my planet a rich mixture burns cooler....and extreme lean condition is what causes manifold overheating, as the unburnt, air deprived mix in the cylinder tries to continue burning into the manifold on exhaust stroke.... I'd be looking for a throttle position sensor fault, blown FPR, something that would cause excessive lean condition....if he were rich he'd be blowing sheets of soot out the exhaust... It's very possible the Cat is stopped up totally too, that'd explain why it won't rev... Signaturejeffcoslacker http://www.automotiveforums.com > I don't know about you guys, but on my planet a rich mixture burns > cooler....and extreme lean condition is what causes manifold [quoted text clipped - 10 lines] > -- > jeffcoslacker It's very possible we are not on the same planet as you. I dropped the exhaust pipe from the manifold and it didn't change anything. Regarding the lean vs. rich issue; you can definitely smell the slobbering. I suspect it's detonation/burn in the manifold. I'll look into the TPS too! > I dropped the exhaust pipe from the manifold and it didn't change > anything. Regarding the lean vs. rich issue; you can definitely smell > the slobbering. I suspect it's detonation/burn in the manifold. I'll > look into the TPS too! It isn't the fuel mixture. If the fuel can't burn in the cylinders it is going to burn in the exhaust manifold unless there is something causing it to burn there like late ignition timing or late valve timing or both. -jim >> I dropped the exhaust pipe from the manifold and it didn't change >> anything. Regarding the lean vs. rich issue; you can definitely smell [quoted text clipped - 4 lines] > going to burn in the exhaust manifold unless there is something causing > it to burn there like late ignition timing or late valve timing or both. Advanced valve timing, not late valve timing, can cause fuel to burn in the manifold, i.e. the exhaust valve opens early while the mixture is still well alight in the cylinder. Late valve timing would have the opposite effect. SignatureDave Baker www.pumaracing.co.uk Usenet - a collection of people who only open their mouth to change feet. >Advanced valve timing, not late valve timing, can cause fuel to burn in the >manifold, Bullshit. It would ping, and maybe pop back through the carburetor. Signature-john wide-open at throttle dot info >>Advanced valve timing, not late valve timing, can cause fuel to burn in >>the [quoted text clipped - 3 lines] > > It would ping, and maybe pop back through the carburetor. Valve timing not ignition timing you pillock. Learn to read. SignatureDave Baker www.pumaracing.co.uk Usenet - a collection of people who only open their mouth to change feet. >>>Advanced valve timing, not late valve timing, can cause fuel to burn in >>>the [quoted text clipped - 5 lines] > >Valve timing not ignition timing you pillock. Learn to read. I'll give you a pass, this time. A jumped tming belt/chain is a different issue altogether. And I am not Polish. :-) Signature-john wide-open at throttle dot info >Dave Baker >www.pumaracing.co.uk Cute ... a.shole. Leave a valid email address next time. =plonk!= Signature-john wide-open at throttle dot info > >> I dropped the exhaust pipe from the manifold and it didn't change > >> anything. Regarding the lean vs. rich issue; you can definitely smell [quoted text clipped - 8 lines] > manifold, i.e. the exhaust valve opens early while the mixture is still well > alight in the cylinder. Late valve timing would have the opposite effect. Maybe, but advanced valve timing doesn't seem likely to happen due to normal wear. Typically the symptoms described fit badly worn timing chain/gears. That may well be due to the ignition timing more than the valve timing. But any inefficient combustion that leaves fuel and air in the correct mix in the exhaust manifold could cause the symptoms described. Especially if the driver's response to loss of power is to use more throttle. So driving 80 mph with a couple of bad spark plug wires could produce the results the original poster described. -jim > -- > Dave Baker > www.pumaracing.co.uk > Usenet - a collection of people who only open their mouth to change feet. You could be describing a loose intake or exhaust or both manifold. It is either running lean which heats things and/or it is burning the excess gas the computer via the O2 is dumping in, in the exhaust manifold. If you spray carb cleaner or even WD40 along the manifolds' gaskets and the engine 'sees' it with a reaction, you have it figured. Just my guess.... Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > I dropped the exhaust pipe from the manifold and it didn't change > anything. Regarding the lean vs. rich issue; you can definitely smell > the slobbering. I suspect it's detonation/burn in the manifold. I'll > look into the TPS too! >if he were rich >he'd be blowing sheets of soot out the exhaust... > >It's very possible the Cat is stopped up totally too, that'd explain >why it won't rev... A slightly rich mixtire won't blow soot, but that, combined with retarded timing, will heat teh exhaust manifold to dull red. ALso, severely retarded timing keeps the enginine from ever being able to rev to redline. Retarded in teh range of 45 to 90 degrees. Engine runs, but poorly, lacks power, poor acceleration, hot exhaust manifold. It's not valve timing if compression checks OK. Signature-john wide-open at throttle dot info >I don't know about you guys, but on my planet a rich mixture burns >cooler....and extreme lean condition is what causes manifold >overheating, as the unburnt, air deprived mix in the cylinder tries to >continue burning into the manifold on exhaust stroke.... It's already burnt. A rich mixture finishes burning in the exhaust manifold, because of air injection (smog pump [or gulping valve on many 4 cyls]). The unburned HC and H2 + CO burns there. Lean mixtures tend to leevae excess O2 and H20, with the balance C02. Try and get THAT mixture to burn by adding air at high temps. :-) Signature-john wide-open at throttle dot info >weeks] until it would hardly move. Any throttle movement would stall >the engine. And the exhaust manifold was red hot before I chose not to [quoted text clipped - 4 lines] >and connectors OK ... where do I look next? Should I tear into the >distributor? .. what should I look for? Late ignition timing. Signature-john wide-open at throttle dot info >>weeks] until it would hardly move. Any throttle movement would stall >>the engine. And the exhaust manifold was red hot before I chose not to [quoted text clipped - 6 lines] > >Late ignition timing. That's what I said, but some are not happy with the simple and obvious -- they want to make it complicated. Don www.donsautomotive.com >It's a 91 2.5L TBI ... the rig became progressively sluggish [over >weeks] until it would hardly move. Any throttle movement would stall [quoted text clipped - 5 lines] >and connectors OK ... where do I look next? Should I tear into the >distributor? .. what should I look for? I had something similar happen to me. Turned out to be a broken ignition rotor. So I would start by looking at the ignition system. ------------- Alex |
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.