My car will randomly jump up about 500 RPMs for no reason. It seems mainly to happen when im slowing down but it will do it at idle too. It makes me nervous because when Im at a stoplight it will jump up and the car will pull itself forward.
Josh Ferry wrote:o2 sensor
Umm no, no possible way
- 2004 Cavalier - 124k, owned since new
Uusually a surge is caused by a vacuum leak, but that also gives a high idle which you didnt mention.
I've seen a TPS sensor cause a surge before though.
The TPS is a wire three sensor, basically a position sensor, it has a resistor in there as well, the TPS is always given 5v, however throttle position depends how much voltage is going back to the PCM
.7V is closed throttle
4.7v is wide open
If your TPS has a glitch in is, like say it goes from 2.5 then to 2.9, and misses that .4 of volts, like it the resistor has a dead spot, it can cause a surge.
Two ways to test, scanner, or a multimeter
Multimeter you need two people though
You need to connect one lead to battery negative, and the other to the TPS wire going back to the PCM, not the 5v refernece or the ground, its needs to be on the signal wire.
Have a buddy sit in the car, with the key on,not started, you watch the multimeter while he goes up and down with the gas pedal, watch as the volts go up and down,and look for a glitch
good luck and hope this helped,and also the above poster with o2 sensor response, an o2 sensor is used for fuel metering,not for throttle control
- 2004 Cavalier - 124k, owned since new
I had the car on a scanner for like 20 minutes driving around last night but it wouldnt do it. Its really random and there really seems to be no reason to it.
it seems like a lot of people have this problem myself included, but the main thing ive heard about this problem is its probably a bad IACV.
WildCard wrote:it seems like a lot of people have this problem myself included, but the main thing ive heard about this problem is its probably a bad IACV.
I dont know about older ones, but newer j-bodies dont have an IAC valve
- 2004 Cavalier - 124k, owned since new
Well say I were to have an IAC valve where would it be on a 99 2200?
Back from the dead. But the surging has gotten worse and has a new symptom. When the wheels are at full crank or when I shift into reverse the RPMs drop low and the car acts like its going to stall out. My friend drove it the other day and he noticed it without me telling him about it. So I assume thats not normal operation.
I do have an IAC according to the Haynes manual.
Could a slipping belt cause a surge? Mine is a little looser than stock since I have a smaller pulley on the alt.
Edited 1 time(s). Last edited Wednesday, May 19, 2010 12:28 PM
