car question

[bobsledder]

I have a 1995 Buick with the 3.8 liter engine. Sometimes when you start it the engine will idle at about 1500 instead of a normal idle of 900. If you push the accelerator the engine will stay at around 3000 rpm. I unhooked the vacuum controlled cruise control , and it did not help. If I shut the engine off and then restart it the idle will be at 900 and it will run fine. The foot feet and linkage all seem to work properly. What might the problem be ?
Bob

 

[wags]

Bob if you start it up does it EVER idle down to 900-1000rpm's on its own or does it stay that way forever or until you do what you spelled out? It is normal for a "cold" engine at start up to idle a bit higher until it "warms” up (it’s the whole choke thing).

My guess is it's a computer thing based on a sensor input if in fact it does not idle down by itself.

I would move this thread over to the Tech section.

Good luck,
Wags

 

[rmk4ever]

Well I would first start looking at all grounds & clean & insure there is a possitive connection. Sometimes when batts. start to go you get weird driveability problems. Otherwise look at all sensors that have to do with fuel-air I.E. mass air flow, intake air temp, throttle sensors.

 

[rp7x]

high idle

clean the sludge out of throtle body and idle speed motor

 

[chitown sledhead]

clean the sludge out of throtle body and idle speed motor

+1
idle air control motor they get carboned up and stick (controls engine idle) remove it clean with carb cleaner and reinstall it dont turn the key on with sensor out of throttle body .Good luck..

 

[lenny]

engine light is not on?

 

[bobsledder]

Thanks for Replies

The engine light came on once, I will have the code read soon.

I will clean the intake and check battery connections after having the code read.

It never has idled down to 900 after starting at 1500.

Thanks again. I'll keep you all posted.

Bob

 

[snow_monkey]

+1
idle air control motor they get carboned up and stick (controls engine idle) remove it clean with carb cleaner and reinstall it dont turn the key on with sensor out of throttle body .Good luck..

X'2 common. Sometimes you can bang on them and get them to break free. There is a spring inside and sometimes you can clean it with carb cleaner. Careful if you remove the unit some have a gasket you will need to replace and also do not clean the area where the gasket was with an abrasive it may be aluminum and you can do damage, 3m wheel is best to prep the surface for a new gasket.

 

[dmsrx]

Check it for a vacumn leak, lean condition will give it a high idle.

 

[bobsledder]

update

The issue is probably the computer. When the car is started and the idle is not correct we shut it off start it again and if the idle is correct it runs normaly.
Bob