Idle Question

[velocedoc]

As a followup to my other post about the anti lock light going on and off, last night at the gas station something odd happened to the idle. I was sitting waiting for a gas pump to come open with the car idling. Suddenly the car's idle jumped up to 1300 rpm and went back to idling at 800 rpm. Really caught me by surprise. The first time I have encountered this condition.

Any one experienced this before and why just once as it hasn't happened before or after.

[elite38868]

Sounds to me like your low speed fan came on and the engine compensated for the initial power up and then went back to normal idling. Try this: get your car good and warmed up, then turn the full lights on and you'll hear the relay click, but you should also see the tach jump a little.

[velocedoc]

I was suspecting that the idle dropped below the initial value and the computer caught it. If the voltage dropped off due to the fan kicking in then the idle would have been part of that. Good thought...Thank you

[BlackAlfa]

Regarding to idle jump, have you cleaned the idle control valve lately? Perhaps it binds a little and does not rotate freely!

Regarding to the low speed fan, it should not cause significant voltage surge or sag when it comes on and off if the electrically system (and battery) is healthy - unless the fan does not turn freely (e.g. bad bearings). Try turn the fan with your finger when the engine is off and cold to see how easy you can spin it.

[Denny164l]

Hey check this out my car when I fire it up in the mornining it fires up and you know the normal rev and then it falls all the way down to 500 or lower almost turning off and then jumps back up again. I dont really pay much attention because its an old engine and when it warms up it runs fine, revs good. only does it when its been sitting for awhile lets say overnite when it cools down alot. Im thinking maybe its the tempsensor on waterpump, because Im also getting the 1223 code on the O2 sensor maybe to lean on cold start?

[BlackAlfa]

Quote:

Originally Posted by Denny164l Hey check this out my car when I fire it up in the mornining it fires up and you know the normal rev and then it falls all the way down to 500 or lower almost turning off and then jumps back up again. I dont really pay much attention because its an old engine and when it warms up it runs fine, revs good. only does it when its been sitting for awhile lets say overnite when it cools down alot. Im thinking maybe its the tempsensor on waterpump, because Im also getting the 1223 code on the O2 sensor maybe to lean on cold start?