Idle problem...HELP PLEASE
12-02-2005, 01:19 AM
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Idle problem...HELP PLEASE For the past several weeks my car has been sitting at 1500rpm when iam at idle at a light. This only happens after I take it to high speeds like a normal drive on the freeway then I exit onto surface streets in stop & go traffic.
If I take the car on the streets, and do granny shifting and not drive the car hard it wont happen??? My SES light also came on so I figured it threw a code for my problem, and it did, the throttle position sensor(tps) so I went to the local chevy dealer and bought the part($65) replaced it my self(easy) and it still has the same problem
What do I do? I did notice that there is another type of sensor in the same are as the tps, but not sure if I should spend the dough for nothing, like I did for the tps>?
Any help would greatly be appreciated.
If I take the car on the streets, and do granny shifting and not drive the car hard it wont happen??? My SES light also came on so I figured it threw a code for my problem, and it did, the throttle position sensor(tps) so I went to the local chevy dealer and bought the part($65) replaced it my self(easy) and it still has the same problem
What do I do? I did notice that there is another type of sensor in the same are as the tps, but not sure if I should spend the dough for nothing, like I did for the tps>?Any help would greatly be appreciated.
12-02-2005, 05:31 AM
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That other "sensor" isn't actually a sensor.....it's the IAC (Idle Air Control) motor. If it's going bad, that could explain your issue. But there are quite a few things that can cause a hanging idle, especially with a setup including as many mods as yours. I'd say try a search on idle and some related words and read through some of the possibilities.
12-02-2005, 07:51 PM
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You need to check voltages instead of swapping parts...
the tps operates on a 5volt reference signal from the pcm, and a ground..the signal returned to the pcm will be between 0 & 5 volts...5 volts (or close to it) = wot.
I'm not at work so I don't have the specs handy, but the tps should be under a volt at idle on most GM products, typically anywhere from .65 - .90 volts
Which tps dtc set?...there can be several, and at least 2...voltage high or low....likely it was high, corresponding to the high idle...check the voltage when the problem is occuring and when it is not, and note any difference...if it's higher when the idle is high, you likely have a mechanical throttle issue....not fully closing (since the tps has already been replaced)
Try to look at the system in a logical manner...the tps merely reports the throttle angle to the pcm...as long as the sensor is good and there is 5 volts and a good ground present, the throttle must not be closed fully if the voltage is high.
Does the dtc still set after tps replacement?...if not, then there are a multitude of possibilities for high idle, the most common being a vacuum leak.
Happy hunting, hth.
the tps operates on a 5volt reference signal from the pcm, and a ground..the signal returned to the pcm will be between 0 & 5 volts...5 volts (or close to it) = wot.
I'm not at work so I don't have the specs handy, but the tps should be under a volt at idle on most GM products, typically anywhere from .65 - .90 volts
Which tps dtc set?...there can be several, and at least 2...voltage high or low....likely it was high, corresponding to the high idle...check the voltage when the problem is occuring and when it is not, and note any difference...if it's higher when the idle is high, you likely have a mechanical throttle issue....not fully closing (since the tps has already been replaced)
Try to look at the system in a logical manner...the tps merely reports the throttle angle to the pcm...as long as the sensor is good and there is 5 volts and a good ground present, the throttle must not be closed fully if the voltage is high.
Does the dtc still set after tps replacement?...if not, then there are a multitude of possibilities for high idle, the most common being a vacuum leak.
Happy hunting, hth.
