Question about 1990 Jeep Wrangler

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1990 Jeep Wrangler: Dies out at low RPM's, at stoplights,backfire

1990 Jeep Wrangler, 6 CYL. 4.0 litre engine, 239,000 miles These are the parts that have recently been replaced: Spark plugs, rotor, distribtuor cap, coil, battery, battery cables, pulleys. Current Symptoms: Jeep starts, but backfires and cuts out at low idle. If you put your foot in the pedal and keep the rpm's up it runs, but the minute that you let off the clutch and come to a stand still it dies. I have disconnected the hose going to the EGR valve in hope that would help the problem, and taken a pressure reading from it(the hose) with a vacume gauage, which showed a CONSTANT pressure of 15lbs at ALL TIMEs going into the EGR valave. I have cleaned the carbueratur with cleaner, advanced the idle, played with the air/fuel mixture all with no change in results. At stoplights I have to rev engine or it dies, when I shift into 1st gear it often dies out. I rely on it for transpo AND I SLEEP IN IT!(Homeless yes it sucks!) I run 89 octanre gas in it. Can you help me? hi  do you think it could be the carberator?

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I had a very similar problem with a 1990 Wrangler with the 4.2L six - Carter carburetor. Another website suggested checking the idle tubes in the carburetor that turned out to be my problem. One indication is that if the curb idle is set way up to keep the engine from dieing, adjusting the idle screw does nothing (no idle fuel is being supplied). To clean the tubes, it is possible to remove the top or air horn component of the carburetor without removing the carb from the engine. Some linkages have to be removed and some hoses disconnected. It is a little tricky but can be done. A book such as Chilton's is good for some guidance. The venturi cluster can then be removed from the main body (still on the engine) by removing a couple of screws. The two tubes hanging down from the venturi cluster are the idle fuel pick-up tubes. I could see these to be clogged at their lower end. There was also a lot of gunk at the bottom of the wells they draw from. I cleaned the tubes with some fine wire, compressed air and solvent. I also cleaned inside the wells as best that I could. Getting the air horn back on is a little tricky - mainly getting the metering rods reset into the metering jets (the two brass rods that hang down from the air horn body. This is facilitated by removing the bowl vent cover and manipulating the tops of the brass rods until they drop into the metering holes. Another option is just to get a carb overhaul kit and remove the whole carb and rebuild it according to instructions. I will probably do this eventually but have fixed it for now.

Posted on Jun 11, 2009

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Check the valves on the #1 cylinder at top dead center both valves must be closed
backfiring is usually a symtom of timing chain/belt slip

Posted on May 28, 2009

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1990 Jeep Wrangler

Many large auto parts stores have loaner meters to read out error codes. They loan them free. The spark being advanced too much for what ever reason would have the same symptom as the timing belt/chain slip
Some things to consider;

) ECM computer. ( used ones are available at auto salvage)
) Check your PCV valve along with the lines attached to it, make sure they are clean. Double check all the vacuum lines on the carb too
) ignition control module
) Compression check on cylinders for bad valves.
) Cankshaft position sensor (CPS)
) carter carb
) Camshaft position sensor (CMS)

Posted on May 29, 2009

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SOURCE: 1990 Jeep Wrangler: Dies out at low RPM's, at stoplights,backfire

It sounds like an intake air ( vacuum ) leak, or ignition timing. Was it doing this before you changed all the above? Or did it start after?
Check all the intake mounting bolts, and carb bolts for tightness. Use a lenght of fuel hose against your earto listen for leaks while the engine is running. A hissing sound will be heard if it's leaking. Wiggle all the hoses with the engine running. You might get lucky and make one hiss at you. A soapy water solution will also detect leaks. ( use hot).
It also could be a leaking egr, or plugged pcv valve, or air filter clogged, or leaking head gasket, bad timing chain, or your camshaft lobes could be worn.
You'll just have to keep looking, and stay calm. It'll feel good when you find it!

Posted on Apr 24, 2009

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It sounds like an intake air ( vacuum ) leak, or ignition timing. Was it doing this before you changed all the above? Or did it start after?
Check all the intake mounting bolts, and carb bolts for tightness. Use a lenght of fuel hose against your earto listen for leaks while the engine is running. A hissing sound will be heard if it's leaking. Wiggle all the hoses with the engine running. You might get lucky and make one hiss at you. A soapy water solution will also detect leaks. ( use hot).
It also could be a leaking egr, or plugged pcv valve, or air filter clogged, or leaking head gasket, bad timing chain, or your camshaft lobes could be worn.
You'll just have to keep looking, and stay calm. It'll feel good when you find it!

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