Cold idle???
#4
Herp Derp Jerp
Join Date: Nov 2011
Location: Parham, ON
Posts: 18,251
Likes: 0
Received 12 Likes
on
11 Posts
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
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!
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!
#5
Junior Member
Join Date: Apr 2012
Location: SW of Wichita
Posts: 51
Likes: 0
Received 0 Likes
on
0 Posts
Year: 1997
Model: Cherokee
Engine: 4.0
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.
#6
Herp Derp Jerp
Join Date: Nov 2011
Location: Parham, ON
Posts: 18,251
Likes: 0
Received 12 Likes
on
11 Posts
Year: 1999
Model: Cherokee
Engine: 4.0L OBD-II
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.
Trending Topics
Thread
Thread Starter
Forum
Replies
Last Post
Zerocyde
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
45
06-29-2022 05:51 PM
tristanp
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
2
09-15-2015 04:06 PM
bufbarnaby
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
11
09-14-2015 09:14 AM
15XJ
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
7
09-10-2015 11:17 PM
BlvdKreeper
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
8
09-08-2015 04:03 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)