Engine Stumbiling

[rdarrin]

My 1998 Jeep Wrangler 4.0 6cyl. is having a problem. just shortly after starting it, the engine stumbles, rpms drop. when i try and give it gas it doesnt respond, it just backfires. the engine does not seem to stall completely, but comes very close. the whole process only lasts about a minute then it runs fine except for it sounds like it is missing during idle. this happens just about every time i start it even after only sitting for a couple of minutes. i tried replacing the disributor cap and rotor, and air filter, but it did not help. the catalytic convertor and sparkplugs and wires are only about a year old so i dont think it is that. there is no check engine lights or fault codes present.

[knelleken]

i would check your spark plugs anyway and if they are not the same as factory, replace with the originals. also, check your fuel pressure(while the problem is occurring) replace your fuel filter(if its not in tank)

[rdarrin]

thanks.. i will check the plugs. im hoping that it is not the fuel filter because it is unaccessible without removing the tank.. i started it today and the engine acted a little different, it loped for about a minute before returning to normal..

[rdarrin]

nope, not the plugs... pulled the old ones out, they indicated normal coloration. i replaced them anyways... checked the ignition solonoid today by measuring resistance, and it checked sat... could this be an o2 sensor.. my rear sensor was replaced about 6 months ago when i had my cat. conv. replaced, but the forward one i have never replaced... would this cause the engine to lope while trying to apply gas shortly after start up and then fix itself?

[tomvid]

o2 sensors will make your engine stumble, hesitate and sputter. If I was you, I would try the idle air control module. That would cause your engine rpm's to go crazy.

[rdarrin]

well i replaced the aic... it was pretty dirty, but i still have the same problem.. not really sure where to go from here

[accutechautomotive]

spray the spark plug wires with water and see if it get worse if it does change wires

[spytearbite]

Could be a pick up module in the distributor. Could be a dirty front 02. Did you add any additives to wash the 02 trying to solve a minor air leak is did you check the intake manifold for an air leak?

Start with a cold engine and spray contact or brake clean around the throttle body base so the spay either raises the rpm or stalls the engine is there are a few places to try on top of what was good info above.