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Jeep Cherokee: Idle air control valve problem on 4.0L six cylinder - READ ONLY

15 messages,  Last post on Jun 02, 2004 at 10:08 PM

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What is this discussion about? Jeep Cherokee, Engine, Fuel System, Fuel Efficiency (MPG), SUV

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#6 of 15 by 0patience Oct 02, 2003 (6:44 pm)
Well, enough said then.   Replace with an OEM (factory) IAC and I think you will find your problem gone. Anytime you buy aftermarket electrical parts (with some small exceptions), you might as well burn your money. I know they have a lifetime warranty, all that means is you spend a lifetime replacing them.
#7 of 15 Erratic idle speed in park by cobrajet7 Oct 04, 2003 (6:19 am)
I have a 92 Jeep Cherokee, 4.0L. It has suddenly picked up an erratic high idle while in park. All vacuum lines seem to be ok, and the throttle linkage looks good. I just read about the idle air control valve here...where on the engine is that located? Perhaps my problem is that, or carbon buildup somewhere. Thanks.. Cobrajet7
#8 of 15 High erratic idle by desi501 Oct 04, 2003 (1:32 pm)
You could have carbon but it's sounds a lot more like a vacuum leak. Can you hear any hissing noises? The IAC is a round unit with an electrical plug held into the throttle body in by 2 screws. Be careful, you can damage it easily. Look for the vacuum leaks first.
#9 of 15 High idle on 92 Cherokee by cobrajet7 Oct 05, 2003 (10:19 am)
Thanks Desi501. We have looked hard for a vacuum leak, but cannot find one. All ports and hoses appear open and clean. I sprayed some gumout at the air intake, and the slot that is near the IAC. No change. Have not removed IAC. I agree, it sounds more like a vacuum leak. Will keep looking at hoses. Cobrajet7
#10 of 15 vacuum leaks by desi501 Oct 05, 2003 (1:51 pm)
Listen closely. You'll usually hear them but look at things like hoses and rubber elbows and connectors. I would think that if that IAC was sticking enough to do that it would set a code and put on the "check engine" light. Even a bad enough vacuum leak will set a lean O/2 code when the computer hits it's limits. You have an OBD 1 system so it's a little more basic than the new ones.
#11 of 15 Idle speed on 92 Cherokee continues to be erratic/high by cobrajet7 Oct 14, 2003 (6:52 am)
We've checked all the vacuum lines, and they look ok. I was told to check the idle air motor (sensor) or the throttle position sensor, both at the base of the throttle body, both accessible and both about $60 dollars each. Any ideas on how to check these parts, and which would likely cause the high idle? The idle speed increases as the engine warms up, and usually runs around 2000 RPM in park. When shifted to drive, the idle is normal. Thanks.
#12 of 15 Unlikely by desi501 Oct 14, 2003 (2:52 pm)
If the IAC or the TPS were sticking they would most likely set a code and turn on a check engine light. They are three wire sensors and can be checked with a digital multimeter. It would take a while to explain the procedure. A bad TPS would give you more of a richer mixture and not an RPM problem. The IAC is the component that controls the idle but when there is a problem there, you usually get stalling, not high idle. Without a scanner it's hard to look at all the things you should be looking at. I still say the MOST likely is a vacuum leak or incorrect base idle adjustment and if nobody messed with the base idle screw the problem probably isn't there.
#13 of 15 Erratic high idle by stridermyth Oct 31, 2003 (10:56 pm)
Hello, Folks. I have a '89 Jeep Cherokee with the 4.o L six cylinder engine with about 160K miles. Recently I've had an increase in a similar problem described in this thread. Only difference seems to be the randomness of occurrence which lately has been more frequent. I suspect the air idle control valve or a vacuum leak. The problem is the engine runs fine for days or weeks at a time. Then one day I'll drive a couple of short one or two mile trips - shutting off the engine for a few minutes between trips - before it happens again. I'll start the engine and it races at high revs. Re-starting don't work unless I wait an hour or so. Your thoughts - please.
#14 of 15 by desi501 Nov 02, 2003 (4:26 pm)
Quote I suspect the air idle control valve or a vacuum leak.   Me too. More likely IAC than vacuum. That won't come and go as much.
#15 of 15 re-opened by request by Sylvia STAFF Jun 02, 2004 (10:08 pm)

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