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Idle setting on 4.0 TJ

My idle has decided to run amok. My Jeep mechanic guru has swapped out the "idle air control motor" and it seems to make no difference. The engine will idle properly in the 6-700rpm range for a while then it will surge to anywhere between 1000 and 2000rpm and remain there indefinitely. The only way I have been able to limit the rpms to a manageble range is by blocking off a major part of the "idle air control passage inlet" (ref. page 14-45, SERVICE MANUAL , JEEP WRANGLER). Can anyone suggest a procedure to isolate and identify the problem? tia dw

Reply to
Dalewhite
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I would guess a dirty connection on the TPS. Maybe give it's plug and socket a quick clean with WD40.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Dalewhite wrote:

Reply to
Mike Romain

Thanks Mike., I'll give it a squirt

Reply to
Dalewhite

Reply to
L.W.(ßill)

The first thing I would suggest is to clean the throttle body REALLY well. Pay special attention to the IAC motor and the port it sits in

- they crud up easily. Also pay particular attention to the area just under the throttle plate - it builds up a ridge. While you're at it, clean the plugs for the TPS and the IAC. The biggest part of my idle problem was cured by those three things (the rest took a few months and a few more parts ).

Reply to
Will Honea

Reply to
Will Honea

Reply to
L.W.(ßill)

Reply to
mic canic

mic canic did pass the time by typing:

Try this.

Backprobe (i.e. don't disconnect) the center pin on the TPS sensor. Measure the voltage with the ignition on, engine not running.

It should be >200 milliVolts with the throttle closed, < 4.8 Volts with the throttle wide open, and butter smooth as you change between the two.

If it jumps it's toast.

If you don't get a good high reading, measure the outer two wires. Should have 5V on them. (don't short these wires or you will frag the computer)

Reply to
DougW

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