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Cold idle???

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Old 01-13-2013, 09:31 PM   #1
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Default Cold idle???

I have a 95 XJ 4.0. auto

How many RPM's should it idle when cold?
Idle's fine when warm but until them it runs 2000-2200RPM's
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Old 01-13-2013, 10:47 PM   #2
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Usually about 1000 till it warms up a little then drops to about 700
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Old 01-14-2013, 07:13 AM   #3
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Ok, so what could be wrong?
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Old 01-14-2013, 07:34 AM   #4
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My 1999 sits at 1000 for about a minute when really cold before dropping to 750.

What your have can be caused by a couple of things. The first thing I'd check for is a vacuum leak. There are two easy ways to test for this: With the engine off, blow smoke into the intake. Fix where smoke comes out! Might be a challenge to get a good seal. The other way is to spray some carb cleaner at possible leak areas while the problem is occurring. The engine will suck in the cleaner through the leak and the idle will sometimes drop or jump as it burns it off. TB and related gaskets, the intake/exhaust manifold gasket, and all vacuum hoses are suspects. Whatever it is would get enough heat to expand after a few minutes and not leak.

The other possibility is that your TPS and IAC are dirty. These two are used to set the idle RPM. These are the units on the throttle body opposite the cable linkage (closest to driver) and on the right side (closest to engine). I recommend just pulling the entire TB assembly and cleaning it. Do a search on here for details if you need them, basically gaskets can be reused if they aren't broken, you need various screwdrivers, a toothbrush and some TB cleaner spray. As well you can test the TPS for correct function (also a few writeups on here).

Tip for searching: in-site search blows chunks. Add "site:cherokeeforum.com" in Google and you'll get much better results.

Let us know how it goes!
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Old 01-14-2013, 08:24 AM   #5
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Quote:
Originally Posted by salad View Post
My 1999 sits at 1000 for about a minute when really cold before dropping to 750.

... TB and related gaskets, the intake/exhaust manifold gasket, and all vacuum hoses are suspects. Whatever it is would get enough heat to expand after a few minutes and not leak. ...

Fuel injector o-rings can cause a cold high idle too (at manifold ports). Found that out when I installed new o-rings with my injectors. The old ones were more like hard plastic than pliable rubber. Probably only sealed up fully after the engine made operating temperature.
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Old 01-14-2013, 10:11 AM   #6
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Quote:
Originally Posted by kansas-klx View Post
Fuel injector o-rings can cause a cold high idle too (at manifold ports). Found that out when I installed new o-rings with my injectors. The old ones were more like hard plastic than pliable rubber. Probably only sealed up fully after the engine made operating temperature.
That's a good suggestion. They can also cause fires, too! A vacuum leak check with carb cleaner should pick up on this.
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Old 01-14-2013, 11:47 AM   #7
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Ok, so what could be wrong?
I think you should pull your throttle body off and give it a good cleaning then go buy a new gasket for where it bolts to the intake manifold
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Old 01-15-2013, 07:58 PM   #8
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I sprayed some TB cleaner in it today, I think it helped, I'll c for sure tomorrow,

If it helps it I will pull the TB off for sure
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Old 01-15-2013, 08:06 PM   #9
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Pull it completely off, clean it and put a new gasket on
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