OffRoadOhio Posted February 23, 2011 Share Posted February 23, 2011 I searched and found similar problem but none that matched my identical issue. Ive also tried some fo the suggestions in those threads with no luck 90 cherokee 4.0 L auto Ive been fighting this issue for over a year, here is the story so far. Jeep developed a rough idle when warm, then eventualy it started dying when you would let off the gas while driving, and when comming to complete stops. I learned to keep it running by putting it in N and holding the throttle at approx 1200 rpms until stopped. If it dies and you restart it it idles fine, but it will not idle if you give it gas and then let off. I thought TPS. I replaced it, and it cured nothing. I unplugged the TPS and the problem went away. But with the TPS unhooked it idles rough when cold and has a dead spot in it. I figured that meant the new TPs was bad. So I replaced it with a differant brand. Problem stayed the same, again I unhooked the TPs and it runs fine once warm now. I have messed with the EGR, I unplugged the vaccum hose while at idle and no changes there and I can watch it move in and out when I rev the engine. I removed the IAC and it moves in and out when you turn the key on, I started ti without the iac in and it moved out to try to compensate for the air flow. I left the IAC unplugged with TPs plugged in and the issue stayed the same with no other effects. Did the same with the EGR valve. I've tried TPs plugged in with both the IAC and EGR un plugged, problem is still there. What am I missing? Link to comment Share on other sites More sharing options...
JeffN Posted February 23, 2011 Share Posted February 23, 2011 Did you clean out the chamber where the IAC sits? I took my throttle plate off and cleaned all the crap out of it and the idle smoothed out alot. I have never experienced your problem though and am not sure if your TPS is adjustable or not. My manual is at my shop so I can't give you voltage specs on the TPS. I noticed you live pretty close to me (I am in Columbus) and I have an Extra throttle plate that has all good electronics on it that I would be happy to let you have. It also wouldn't be a bad idea to replace the gasket under the throttle plate as it could cause a problem. Link to comment Share on other sites More sharing options...
OffRoadOhio Posted February 23, 2011 Author Share Posted February 23, 2011 Yes, I forgot to mention that ive cleaned the crap out of the intake. I even used the "fuel system and intake tune up" stuff that we sell at the shop I work at. It hasnt changed at all. Link to comment Share on other sites More sharing options...
MancheKid86 Posted February 23, 2011 Share Posted February 23, 2011 oxygen sensor :???: I have messed with the EGR, I unplugged the vaccum hose while at idle and no changes there and I can watch it move in and out when I rev the engine. there should be a significant difference when the vaccum hose is disconnected, you may have a leak? Link to comment Share on other sites More sharing options...
OffRoadOhio Posted February 23, 2011 Author Share Posted February 23, 2011 I just had a revalation becuase of that comment. At idle the EGR stays closed when hooked up. When I open it manualy at an idle the engine dies. If I rev the engine it'll open up for a little bit and then close. I wonder if the EGR isnt just sticking open? I havent checked the EGR when it dies, ive only checked it in my garage after warm but while running. Link to comment Share on other sites More sharing options...
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