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nrlewellen47 11-11-2011 03:03 PM

Jeep has problems starting
I have a 2004 jeep grand cherokee with a 4.7 V8 in it, bought it back in february. Two days ago i took out the IAC and cleaned it as well as the throttle body because it was running close to 2000rpms when you would start it up. While I was doing that i went ahead and changed my spark plugs (they were WAY overdue to be changed). Put it all back together, took it for a spin and all seemed fine, idling at about 800rpms. Now it wants to turn over a whole mess of times before it wants to start, I have to pump the gas multiple times before it takes off. Once it gets running and is at idle speed, if you just tap the gas you can hear it hesitate as if it is going to stall before it takes off. It also sounds as if one of the headers might have a hole or be cracked (dont think i noticed this sound before i clean the IAC and changed the plugs...but it could have been there) not sure if that has anything to do with it. It seems to be one thing after another with this Jeep.

I just went back out and listened to the *manifold leak*, and Im pretty sure that is NOT what it is. It makes that sound only at a low idle, between 600-900 rpms. When i rev the engine up to 1000-1200 rpms, this sound goes away. Deos this have anything to do with the starting problem?

Frango100 11-11-2011 05:58 PM

Re: Jeep has problems starting
Are you sure you didn't forget to put back all the hoses? An air leak in fact should increase the idle speed, but you never know.
When cleaning the IAC stepper motor, did you take care to not turn the plunjer? Because when you do, 2 small plastic cams will shear off and the plunjer will most probably not function as required (how do i know that:o). If it turns with the stepper motor, it will not move in or out.

nrlewellen47 11-11-2011 06:20 PM

Re: Jeep has problems starting
I did check all the hoses. When i first put it back together I had missed one so i went back and checked them. The is a good chance I turned the plunger, I had read that you shouldnt push them in and out, but had not heard about not twisting them, I guess that would be a good place for me to start. Thanks for the info, I would have never known.:thumbsup:

Frango100 11-11-2011 09:56 PM

Re: Jeep has problems starting
In fact you can't pull the plunjer out or push it back in. The plunjer has internal thread (kind of spindle like) and the motor external. The 2 plastic cams prevent the plunjer from rotating. When the cams break off (not that much force needed to do so), the plunjer will be free to rotate with the motor and will not open or close the idle air passage anymore.

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