Idles high (2000-2500) when cold, warm is all good

[tom04841]

just as the title says. Cold is really high, but once up to temp it idles fine. ISC changed. Any other suggestions? Maybe coolant temp sensor?

 

[EclipseTrbo420A]

Its normal for a car to Idle high then fall to normal as the motor warms up mine hold at 1700 and slowly goes down to 750 as car warms up.

 

[Quasimondo]

That's perfectly normal. There is nothing wrong with your car. Ignore the man behind the curtain.

All cars have high idle when they're started cold. The high idle helps to warm the engine quickly.

 

[tom04841]

i didn't think that high of an idle was ok.

 

[EclipseTrbo420A]

i didn't think that high of an idle was ok.

I have also seen quite a few 1G's that had a pulsing idle on cold starts. Its just the get the car to opperating temperature quicker. Your fine.

 

[Ruby]

I don't think 2,000-2,500 rpm is normal and I have the same problem. I guess I will take my 91 to the dealer. Yes, 91...I was hoping to find the answer because whatever is causing this is sure to be electronic of vacumm/electric. I will post the results once I get it fix.

 

[Quasimondo]

High idle when cold is normal. The high idle is caused by a device in the throttle known as the FIAV (Fast Idle Air Valve). This valve consists of a wax pellet. When the engine is cold and the pellet is solid, a small bypass is opened up allowing more air into the engine at closed throttle. As the engine warms up, coolant passing through the throttle body melts this wax pellet. When the engine reaches full operating temperature, the melted wax seals off this bypass, returning your idle speed to normal.

High idle when cold is normal. High idle when warm is not normal.

 

[andymoraitis]

High idle when cold is normal. The high idle is caused by a device in the throttle known as the FIAV (Fast Idle Air Valve). This valve consists of a wax pellet. When the engine is cold and the pellet is solid, a small bypass is opened up allowing more air into the engine at closed throttle. As the engine warms up, coolant passing through the throttle body melts this wax pellet. When the engine reaches full operating temperature, the melted wax seals off this bypass, returning your idle speed to normal.

High idle when cold is normal. High idle when warm is not normal.

Great explanation. On a slightly related note when the water temp reaches 122 degrees, the idle control is taken over from the FIAV by the ISC (idle speed controller).

 

[steve]

Great explanation. On a slightly related note when the water temp reaches 122 degrees, the idle control is taken over from the FIAV by the ISC (idle speed controller).

Close Andy, the ISC is always active but the FIAV should be fully closed by the time the coolant temp hits 122F (pg 14-13 1G Tech Ref).

If the idle is pulsating your having idle surge, where the ECU sees that it's idling and is turning off the fuel when the idle speed exceeds the programmed value for the current coolant temp. If it's surging the idle speed is too high. If it's not surging then it may be higher than you like but it's within the factory bounds.

Steve