won't idle down
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Junior User
Joined: Feb 2003
Posts: 55
Likes: 0
From: Alabama
won't idle down
Hello;My 1989 has a 302 with a 4 speed trans.The truck starts fine and it idles down to around 900 rpm.However,say I am at a stop light and I take off in 1st gear and shifting into 2nd gear,when I take my foot off the gas the rpm's won't drop off.It is like the gas peddle is stuck,which it isn't.If I bog the engine down the rpms will come down to at least 1500,then I shut the engine off.I start the engine right back up and guess what,it runs like it should,with the rpms dropping off when I shift from one gear to another.This condition doesn't happen every time I drive it,but it is becoming more frequent.Any idea on what the problem is with my truck. Thanks for all of you help;
Jack
Jack
Senior User
Joined: Jul 2004
Posts: 321
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From: Cold Lake, Ab
Any more suggestions?? Have the same problem on an 89 F-250 302. Mine will Rev up to 3000RPM when I place my foot on the clutch to shift, stay that high if I dont release the clutch or shut the truck off. Shut her off or put it back in gear and its normal again. Mine only does it after a long drive and the motor is good and hot. Normal in town driving no prob.
Also getting worse and doing it more often.
Also getting worse and doing it more often.
Senior User
Joined: Jul 2004
Posts: 321
Likes: 0
From: Cold Lake, Ab
it should do it hot or cold if it where the throttle spring. This only happens when the vehicle as been driven long range or worked hard and its really heated up. Any of the sensors that I should check into that control idle?
Senior User
Joined: May 2004
Posts: 194
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From: Waterford Michigan
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Thread Starter
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Junior User
Joined: Feb 2003
Posts: 55
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From: Alabama
I never gave the TPS or the IAC a thought,because I replaced both of them in March of 2003,to cure the up and down idle problem that I was having,which it did.Today I took off the IAC and cleaned it with throttle body cleaner.To me, it wasn't even dirty like the one I took off in March.It had very little buildup.But,it must have been the cause of my problem because it is now operating like it should.How often should the IAC be cleaned?Thanks for your help: Jack
Junior User
Joined: Dec 2002
Posts: 64
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From: Edmonton Canada
First to make sure that it's the iac, unscrew the solenoid from the base(2 phillips screws) and remove it and the idle should drop to or below normal. If it does do this, just clean the iac plunger and replace the solenoid. When the solenoid is off and the engine is running you can push the rod in and the engine will rev up. I noticed when I replaced mine, I drove with the solenoid off and I noticed when I coasted(decelerated) in gear, the exaust really pops alot. When I replaced it with a different one, all is well..
Senior User
Joined: Sep 2003
Posts: 223
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From: York, PA
Oxygen sensor can cause a high idle, if the oxygen sensor sees a rich mixture, pushing in the clutch allows the engine management to rev the engine and feed oxygen through the IAC to send oxygen sensor low,(like the engine management wants to clear a rich fuel mitxture in the exhaust)I have seen it that the ECM will not lower RPM's until the sensor sends the enriched oxygen signal back to the ECM, then it will lower the RPM's through the IAC. Repair has been to replace the oxygen sensor. Broken Wire
