High idle only at srart up....HELP!

  • Thread starter Thread starter pippo
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pippo

Hi guys,

I am new here, so I am hoping to get some help on this.....

87 sunbird, GT, non turbo, stick shift. For about a few months now, whem the car is started, it idles very high immediately. Much higher (about 3000rpm) when it is cold (say, 45 deg F in FL). I am thinking temp sensor, guess I could spec it our for ohms when hot/cold, but no codes on dash. New items: AIC valve, TPS. MAP is original. Any tips?

Thanks!!
Joe
 
wde3477 said:
Perhaps check for vacuum leaks - particularly the larger vacuum lines such as the brake booster.
Click to expand...

Thanks for the fast advice, wde!! I forgot to mention, the idle goes down to normal upon warming up say, in 5 minutes. Would booster still be suspect here?

Thanks!!
Joe
 
Hmm, a vacuum hose leak is probably not as likely of a cause in this case, its effects should be seen at all times - still worth laying a set of eyes on everything, looking for anything unusual - cracked hose fittings or failed hoses. Kind of going out on a limb a bit, but perhaps there is a leak that seals off as the motor warms - such as an intake manifold gasket???

It looks like you've already replaced the Idle Air Control (IAC) valve - that is the culprit many times for idle speed problems.

Suggest the general problem is that too much air is being admitted into the engine from somewheres - exactly from 'where' is the challenge to find. Whether this be a faulty IAC, vacuum hose leak, manifold gasket leak, PCV valve stuck open, wedged-open throttle butterfly, failed brake booster diaphragm, etc. Has anything else been acting funny that may give a clue?

One trick is to lightly spritz carb cleaner around suspect areas to see if the engine speed picks up. Caution must be used as one is spraying a highly flammable substance out into free space. If you can't figure out what the problem is, then the alternative is to start eliminating what you know the problem isn't.

This can be a challenging problem - only get about 5 minutes to test before the speed drops, then would have to let the engine cool back down in order to re-simulate the problem.

Man, I would love to live in an area where 45degF is considered 'cold' :-)~
______________________________
 
wde3477 said:
Hmm, a vacuum hose leak is probably not as likely of a cause in this case, its effects should be seen at all times - still worth laying a set of eyes on everything, looking for anything unusual - cracked hose fittings or failed hoses. Kind of going out on a limb a bit, but perhaps there is a leak that seals off as the motor warms - such as an intake manifold gasket???

It looks like you've already replaced the Idle Air Control (IAC) valve - that is the culprit many times for idle speed problems.

Suggest the general problem is that too much air is being admitted into the engine from somewheres - exactly from 'where' is the challenge to find. Whether this be a faulty IAC, vacuum hose leak, manifold gasket leak, PCV valve stuck open, wedged-open throttle butterfly, failed brake booster diaphragm, etc. Has anything else been acting funny that may give a clue?

One trick is to lightly spritz carb cleaner around suspect areas to see if the engine speed picks up. Caution must be used as one is spraying a highly flammable substance out into free space. If you can't figure out what the problem is, then the alternative is to start eliminating what you know the problem isn't.

This can be a challenging problem - only get about 5 minutes to test before the speed drops, then would have to let the engine cool back down in order to re-simulate the problem.

Man, I would love to live in an area where 45degF is considered 'cold' :-)~
Click to expand...

Thanks again. Yup...I first might try specing out the 2 sensors mentioned (temp and MAP), then poke around elsewhere.

Sometimes it is so cold here (LOL), I have to cover my coffee trees at night as they do not like it below 45 F.....brrrrrrrr.........LOL!!
 
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