Jeep 4.2 Engine Troubleshoot...really weird - JeepForum.com

 
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post #1 of 6 Old 06-28-2002, 04:58 PM Thread Starter
fatcaaat
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Post Jeep 4.2 Engine Troubleshoot...really weird

I drove my jeep all day. I had two blocks to go and i decided that I would trap the gas from the stopsign. I did and when I slowed down to let the thing idle, it stalled. Fire it up and drive it to the driveway...it won't stay running at idle. I checked and it runs and drives normally at anything above 1200 rpm but will stall out under it. It will start right up but won't idle. The solution is not to raise the idle. Something happened here...any suggestions?

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post #2 of 6 Old 06-28-2002, 05:55 PM
johny1i
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This may be a dumb question, but what do you mean by "trap the gasoline"? One thing that can come up quickly like that is a vacuum leak--it happened to me when my intake gasket developed a leak. Try cupping your hands over the carburetor tightly as if you are trying to suffocate it (with the air cleaner removed)--if it speeds up and idles okay, you are getting WAY too much air from somewhere else.

Currently an '86 CJ-7 and a '77 CJ-7 Golden Eagle---#4 and 5 following a '01 Sahara, '90 Sahara, and '85 CJ-7....
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post #3 of 6 Old 06-28-2002, 06:03 PM
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check for vacuum leak maybe? you might have jolted something by gassing it. the intake manifold gasket and carb base would probably be the first places to check. to see if the problem actually lies in the carb, remove the air cleaner, start the engine and squirt a little carb cleaner into the carb. (you may need someone to fire it up while you are ready with the cleaner) if you can keep it running this way, then more than likely hte pboblem is in the induction(carb, manifold, etc...) the reaeon this works is that you are adding fuel to the incoming air charge. another thing you could check would be the EGR valve. it is only supposed to open at higher rpm's to control emissions by "reburning" the exhaust. it could be stuck open, allowing exhaust gas into the engine at idle. this would lean out the mixture enough to possibly stall. hope these ideas help, they did with my idle woes! jairus

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post #4 of 6 Old 06-28-2002, 10:49 PM Thread Starter
fatcaaat
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Ok. I meant to say that I tramped the gas. Here is the next assessment. I don't have any emissions on this jeep, so scratch anything to do with it. I just went to the garage to make sure it was completely cooled down (5 hours i guess) I pumped the gas 2 times and turned it. It starts and idled fine at high idle. No stumbling or nothing. Perfect. I tapped the idle down and it dies. I will look at the intake stuff tomorrow. What about spraying some carb cleaner around the intake manifold. Will I be able to detect it there?
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post #5 of 6 Old 06-29-2002, 07:44 AM
johny1i
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Yes, definitely spray some around any suspected leak area--I should have suggested that to begin with.

Currently an '86 CJ-7 and a '77 CJ-7 Golden Eagle---#4 and 5 following a '01 Sahara, '90 Sahara, and '85 CJ-7....
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post #6 of 6 Old 06-29-2002, 02:49 PM Thread Starter
fatcaaat
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Thanks all...it was a vacuum leak around the carb. I have a 4-barrel clifford intake with adapter and a weber. The nuts on the adapter and carb were loose. I replaced the gaskets and it purrs like a kitten. Thanks a bunch...what really did it was cupping my hands over the air intake and making it run smooth...then I knew it was a leak. I appreciate all you guys suggestions..
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