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Very High idle, whats the problem?

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14K views 11 replies 6 participants last post by  Shawn R  
#1 · (Edited)
Hey guys, last weekend i started my car, and i noticed that the idle immediately shot up to 2000rpm's. It was cold out, so i didn't think much of it, and just let it sit and see if it settled down. It settled to about 1200rpm's when warm. Usually the car idles at 1200 cold, 700warm. When i drove around, and came to a stop, the idle would go down to around 1000 then slowly rise up to 1300. Sometimes it would go as high as 2000, then drop to 1200. I had to get back to school so i couldn't diagnose it until today when i got home. I started it up and its still idling the same. This happened suddenly, so i dont really know why it happened, so im looking for advice from you guys on what it could be? Thanks!

Edit: forgot to mention that i disconnect my battery during the week while im at school because if i dont, the battery will die (odyssey lightweight). Could the high idle be caused because the ecu was reset? It never did this before when i would disconnect my battery. When i got home today i reconnected my battery, and started it, and it idled the same as last week, really high. I turned it off, and restarted it a few minutes later and now its idling normal. I didnt get a chance to drive it tho cuz the weather is bad right now to see if while driving when i came to a stop if the idle stayed normal, or was acting up like last week. Guess it was the ecu being reset that messed with the idle?
 
A
#2 · (Edited)
vacuum leak?
IAC?
it have happen to me before the sigle and fuel install,( same, just like your, first start up will idle high as high as 2200 rpm and if I shut it off right away and re-start it up it will idle normal again) and I clean the IAC too while it out for the fuel install, so I have no idear what fix it .
 
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#6 ·
I don't believe that this sensor would cause the problem. I believe the computer uses it to turn on the little fans.

Out of curiosity, do you have a check engine light on?
 
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#8 ·
make sure your throttle linkage is properly moving, it can get stuck and keep the throttle artificially high.
 
#9 ·
throttle linkage is working as it should, just checked it.

Its weird because when i start the car for the first time in a few days after having the battery disconnected, it will idle high. Then when i turn it off and wait a while and turn it on again, it will idle normal. This has happened the last 2 times i have started the engine cold.
 
#10 ·
It’s your IAC (Idle air control valve) which regulates and controls air flow when throttle is not open. Due to the cold weather, the solenoid opens to far and can not adjust it self in time until the coolant runs through its two lines and heats the IAC motor up. This is a common problem and confuses the ECU; after it heats up and the car is restarted the ECU reads its present condition and causes the car to run fine on idle. I would check my IAC and clean it.
 
#11 ·
It was around 38 degrees last sunday when this first happened. I only started it once and drove it around, i never turned it off and restarted it. Then i disconnected the battery when i got back home. Then today i reconnected the battery and started it and it was about 70 degrees, and it did the same thing. Then i turned it off and turned it on and the idle was fine. If i clean out the IAC should it fix the problem?
 
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