91 Idle woes continue
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Joined: Feb 2003
Posts: 57
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From: Westfield NJ
91 Idle woes continue
A while back I was having trouble after the car warmed up it would idle like a cylinder was missing and there was a loud knocking. The knocking turned out to be the clutch. I replaced the flywheel-clutch assembly. Now the miss is still there yet not as pronounced. So far I have replaced the plugs, cap, rotor, wires, pcv, inline fuel filter and set the timing. When the car is cold, it runs great. pull away power throughout the whole spectrum. After about 5-10 minutes, the mid-range goes away and the rough idle returns. After I shut it down for a few minutes, it runs great again and then same symptoms! The car has just under 30k on it. (L-98). I have not run a compression test yet. Any other suggestions? Thanks.
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Joined: Feb 2003
Posts: 57
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From: Westfield NJ
Plugs looked fine. 10k Bosch platinums now in the garbage. No codes. Did not do leak down. Also, even though mid-range leaves, after the rpm's go up it seems to clean out. Oh yeah....cleaned intake manifold as well. Frustrating.
6th Gear
Joined: Dec 2005
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I had idle problems with my '91 as well; at idle it was rough, but under a load it would cut out and miss badly. Turns out the fuel pump was going out. Replaced fuel pump, wires, pluge, cap and rotor and it runs as good as it ever has.
Melting Slicks
Joined: Oct 2004
Posts: 2,283
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From: Leeds Alabama
how about actually testing the system instead of throwing parts at it? Module, pick up, IAC motor, Air system,, egr solenoid, have you tried a idle reset proceedure per factory service manual? What about the spark advance , knock sensor? Fuel pressure, tested injectors? Did you ohm injectors?Did you unplug spark advance when you set idle?......
Le Mans Master
Joined: May 2005
Posts: 5,214
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From: Queensland, AUSTRALIA
Does it run strong at wide open throttle regardless of temp??
Pull the lead off the O2 sensor and see if that stops it happening. (which it should)
Then check the EGR system, make sure its not letting exhaust gasses through when its meant to be shut (pull the vacuum fitting off the EGR valve and block it, that should make the EGR valve stay shut)
Check the A.I.R. system and make sure its not pushing air into the exhaust when it shouldnt be, the O2 sensor will see this and think the engine is running lean.
Check the MAP sensor is connected to its vac line with no leaks
Check that the exhaust system has no leaks before the O2 sensor (its on the left bank), leaks could allow air to be pulled in and seen by the O2, causing richening.
Pull the lead off the O2 sensor and see if that stops it happening. (which it should)
Then check the EGR system, make sure its not letting exhaust gasses through when its meant to be shut (pull the vacuum fitting off the EGR valve and block it, that should make the EGR valve stay shut)
Check the A.I.R. system and make sure its not pushing air into the exhaust when it shouldnt be, the O2 sensor will see this and think the engine is running lean.
Check the MAP sensor is connected to its vac line with no leaks
Check that the exhaust system has no leaks before the O2 sensor (its on the left bank), leaks could allow air to be pulled in and seen by the O2, causing richening.
