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Coolhand1 04-06-2007 10:00 PM

YJ buckin like a Mule & my saddle dont fit...HELP!
I seem to be misfiring on the next to last cylinder...1991 renagade 4.0L. Done all the usual things, plugs ,wires, cap,rotor. get a check engine light. Hooked it up to a scanner and got a " no vehicle speed sensor detected under load" But it will reset and I won't get it again until the buckin' starts. Any Ideas? I'm out of them. Thanks

Coolhand1 04-07-2007 08:05 PM

I spoke to a John @ morris 4x4 in Florida he said it could be the electricial conection at the injector and reccomended cleaning the contacts and adding dielectric grease to the connection. I will give this a try and let you know........................

Coolhand1 04-09-2007 11:39 PM

Didn't work but it was worth a try. Am I the only person on the face of the planet that has had this Problem???

Coolhand1 04-27-2007 02:41 PM

I have noticed a back fire between the gears and when I push in the clutch the rpm will drop to around 3 to 4 hundred rpm or the motor will die outright. When accelerating there is a deffinatly a miss because the jeep will hit miss hit miss (AKA BUCK) ant ideas? This is getting real old.

zeus87gn 04-27-2007 02:56 PM

Check for slack in the timing chain. They get old after a while.

jay-h 04-27-2007 06:06 PM

does that cylinder have full compression?

Cobra Jeep 04-27-2007 06:27 PM

Yea, do a compression check.

Monk89 94 I4 04-27-2007 10:42 PM

this is going to sound so silly, but you DID make sure you put the wires back in the right order? can you give us more information about the miss? at a specific rpm? or it just dose it while running?


Coolhand1 04-28-2007 10:13 AM

I have not done a compression check yet, and it seems to miss at low rpm. It will rum fine for a while and all of a sudden start the bucking and I am not for sure if the back fire is constant I only hear it a slow speed. A mech I took it to said that the miss was in the 5th cylinder but he couldn't find the cause???? with the backfire could this be a timing issue?

leftlanetruckin 04-28-2007 10:19 AM

if you didnt move the distributor, i'd doubt it, unless it needs replacing.
you need to do a comp check, and rule out any mechanical issues. the timing gear does wear, but is normally accompanied by a slapping timing chain.
sounds more electrical to me...
you can get a bad plug and lead, so just cause they are new, dont totally rule that out....


Coolhand1 05-05-2007 01:52 PM

Problem Solved!!!!!
It turned out to be the Automatic Idle speed motor.

In my posts I talked about a gummed up AISM, so I replaced it and the jeep was idling at 2500 rpm so I disconected th Neg. battery cable and cleared the ECM. After that the ECM went into a programming mode and retaught its self the position of the AISM comparing the RPM with the seat position dropping 500 rpm at a time, until propre Idle rpm was achived, all of this took about 1 minute. Now the codes are gone and I am happy:2thumbsup:

The time now is 07:27 AM.

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