i'm having an intermittent starting prob with my '93 grand cherokee. there will be a stretch where it won't stay started without any revving until it warms up, then it works fine for a few days/weeks, then more of the same starting problems.

is the throttle position sensor or o2 sensor a possibility? the follow-up q would be, where is a good diy for that?

i know its not a fuel filter, as its been replaced. any other opinions would be greatfully accepted.

thanks for the sage advice, and have a healthy, happy '05!

jackie

I would say that the o2 would not be a factor. the reason is the pcm doesnt really use the o2until it starts to warm up.the tps could be a possibility but it wouldnt be my first guess.It sounds like a possible iac problem,since that is what controls the idle speed.if you have to rev it the iac might not be opening enough.or it could be the battery.if the battery is weak,the pcm loses memoryand then it wont idle.

so the next newbie q would be....what's the iac? thanks for the prompt reply!

idle air control valve or some people call it an idle air control motor.seriously,have your battery tested first.

[QUOTE=xj31]I would say that the o2 would not be a factor. the reason is the pcm doesnt really use the o2until it starts to warm up.

Hi,

Just related to your comment and my particular problem...My '99 GC 4.7 V8 starts to rev at 1500 rpm upon initial cold startup, before settling down to 600 rpm idle. Subsequent starts, after the engine is warm, the engine revs as high as 3500 rpm before slowly settling down. Does this case sound like like an o2 problem? Thanks for your help.

Bob

[QUOTE=xj31]I would say that the o2 would not be a factor. the reason is the pcm doesnt really use the o2until it starts to warm up.

Hi,

Just related to your comment and my particular problem...My '99 GC 4.7 V8 starts to rev at 1500 rpm upon initial cold startup, before settling down to 600 rpm idle. Subsequent starts, after the engine is warm, the engine revs as high as 3500 rpm before slowly settling down. Does this case sound like like an o2 problem? Thanks for your help.

Bob


Most of the issues related to this topic are IAC (Idle Air Control) related or a dirty throttle body. I would try cleaning the throtle body first then investigating replacement of the IAC.

CURBSIDE - your problem would deffinately be the IAC problem, clean the throttle Body thoroughly.

BERBES - XJ hit it on the nose, Idle Air Control Valve (motor).

I replaced my IAC about 2 weeks ago and it did the samething, so I replaced the battery - which has been very close to dead for awhile now and all I got was the fast spinning of the engine that I used to have and missed. So I replaced the IAC valve again 2day and I guess we will know in the next couple days if it helps ot not.

I recommend not buying the IAC from autozone (WELLS brand) get another brand from another store. some Autozone parts are known to be bad out of the box.

how much does the IAC cost?

the IAC I got from autozone was $44