High Idle
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Senior User
Joined: Oct 2004
Posts: 123
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From: Central Jersey
High Idle
Gentlemen,
I again rely on your knowledge and expertise. A few weeks ago I posted a check engine light. Turned out it was the EGR valve (disintegrated, is this common?). Anyway, after replacing the valve, sensor control and associated plumbing and resetting the CPU, the truck runs fine. However, the idle seems a bit higher than before, around 1k, and when coming to a stop in neutral, it sits at 2k for a minute and slowly comes down. Is this normal for a 4.0L manual shift? I don't remember the idle so high before the valve replacement. Any thoughts?
I again rely on your knowledge and expertise. A few weeks ago I posted a check engine light. Turned out it was the EGR valve (disintegrated, is this common?). Anyway, after replacing the valve, sensor control and associated plumbing and resetting the CPU, the truck runs fine. However, the idle seems a bit higher than before, around 1k, and when coming to a stop in neutral, it sits at 2k for a minute and slowly comes down. Is this normal for a 4.0L manual shift? I don't remember the idle so high before the valve replacement. Any thoughts?
Elder User
Joined: Oct 2005
Posts: 623
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From: Blytheville, AR
My idle stays a little high after coming to a stop. (2.5L 5spd) That's to be expected out of a manual shift vehicle. However, normal idle at ~800-900 is what you should expect. The 1k is a little high. Anyone else with a 4.0?
Post Fiend
Joined: Feb 2003
Posts: 6,940
Likes: 2
From: Eastern WA
My old 94 4.0 5spd (OHV engine like yours) consistently idled at 750 rpm when the vehicle was stopped and did so since new. When rolling to a stop, I recall it idled at about 1,000 rpm until the vehicle speed dropped to around 5 mph or so. Provided this new problem appeared after fixing the EGR, I would carefully inspect for any vac leaks.
Post Fiend
Joined: Jul 2005
Posts: 8,462
Likes: 4
From: Durant, OK (SOSU)
I agree with Cowboy, check for vac leaks. I have a manual 4.0L and no high idle. When I go to slow down and first hit the clutch it drops to around 1000, then comes down about 2-3 seconds later slowly to 750 or so, where it will stay. Speed doesn't seem to matter, it'll do this at 20 or 70. (well, a little higher at 70 obviously).
Thread Starter
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Senior User
Joined: Oct 2004
Posts: 123
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From: Central Jersey
Ok guys, I quit!. Checked for vacuum leaks, none found. The TBH was dirty (very), so I hosed it out with TBH cleaner and damaged the IAC. Replaced the IAC. Truck idles better, but still @ 1k, and is slow to come down. Runs great, so I am hesitant to muck around with too much, but is there a way to lower the idle?
Thanks again!
Thanks again!
