godchaser
NAXJA Forum User
- Location
- Connecticut
Does anyone have or ever had a 4.0l that idles very high at times? Mine does it now and then, mostly in the hot months. Any suggestions?
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89 MJ 4.0 periodically idles high
- Thread starter godchaser
- Start date
jeepmonz
NAXJA Forum User
- Location
- muskegon,mi
every now and then and never when I'm anywhere near where I can do a proper diagnosis my 89 cherokee's 4.0 will hit 2000 rpm idle at start up and stay there (it will rev higher with throttle input but won't drop below 2000) until I shut it off and restart so if that is what you have going on then yes someone else has the problem but no I don't know what the cure is yet as I haven't had the time to find out what is wrong with mine.
Doug
Doug
outlander
NAXJA Forum User
- Location
- Columbus,Ohio
maybe the iac is gunked up and sticking causing the plunger not to move into it's bore to controll intake air flow?
5-90
NAXJA Forum User
- Location
- Hammerspace
1) Check/clean throttle body. The IAC and/or butterfly valve can get crapped up and cause weird idle - see my recent posts in another thread (I think Cottontail started that one.) I don't see any need to repeat myself - I gave the highlights of doing the job, since I did two last week-end.
2) Get a can of carburettor cleaner, and have your engine idling. Fog the carburettor cleaner around anything that's a vacuum seal (including manifold sealing surfaces and ANY vacuum lines!) and see if the cloud gets drawn in and the idle jumps up. DO NOT use the little red straw.
3) It's probably worth retorquing the manifold bolts out of hand - I check mine once a year, and I usually catch one that's just a little loose.
If you need vacuum lines, I updated the prices on the sets at NAPA - they should be the same between XJ/MJ.
5-90
2) Get a can of carburettor cleaner, and have your engine idling. Fog the carburettor cleaner around anything that's a vacuum seal (including manifold sealing surfaces and ANY vacuum lines!) and see if the cloud gets drawn in and the idle jumps up. DO NOT use the little red straw.
3) It's probably worth retorquing the manifold bolts out of hand - I check mine once a year, and I usually catch one that's just a little loose.
If you need vacuum lines, I updated the prices on the sets at NAPA - they should be the same between XJ/MJ.
5-90
godchaser
NAXJA Forum User
- Location
- Connecticut
You are right about turning it off, then re starting. I have got to wait about a week though, in the middle of a 4.5 lift / rear oil seal replacement. I will definitely check those items.
jfiscus
NAXJA Forum User
- Location
- Middletown, OH
I recently put a 93 engine into my 89 renix system. I do not have my TPS adapted properly and have experienced this problem intermittently when my TPS gets loose and needs adjusted/tightened. I think that it is getting stuck thinking that the idle is actually a different setting. It was always fixable after turning it off/restarting the jeep, but gets annoying. After reseating my TPS it is fine. Hope this is helpful.
