Mechanics

ALERO V6 3.4 LITER

2001 All Other Makes All Other Models

I am having a strange problem. Normally I am able to troubleshoot and repair most car problem, but this one has me baffled. So i'm turning to you guys for some insight.

This problem starte very suddenly with no explination. Started my car one morning to go to work. Normally the car will idle around 1.5K RPM until warm then drop to 800RPM. This particular morning the car was started and immediately went to 2K RPM and slowly started creeping upwards to 3K RPM until I finally turn the ignition off. I then started it back up immediately, and it began to idle normally, so I took off to work. As I was driving that morning, I didn't notice anything wrong untl I got to an exit ramp to enter the main highway, at this point I always floor my car to merge into the faster moving traffic, when I did, my car actually started to slow down and the RPMS went down, so I started to pump the gas, after about the third pump, the engine jumped to 3K RPM and shifted at 4K RPM. (Normally the engine would coninue to rev up around 6K RPM then shift, and go to 6K RPM again and finally shift into it's final gear) Once I arrive at my exit and merger into the slower traffic, every other time I would have to come to a stop for a traffic light, the engine would just die and shut off. The engine will always start right back up with no problem though. I have investigated a few things, fuel pump, vacum leaks, and computer problem. The check engine light doesn't come on, there are no vacum leaks, and my fuel rails are getting proper fuel pressure. One thing I tried, to try and isolate the problem being either the engine, or transmission, is I shifted manually by starting out with the gear stick in 1st, and punched the gas. I slowly worked up the gears using the stick and it accellerates fine when I use the shifter like that, I put it in 1st, accellerate until the RPMs are around 6K, then shift into 2nd, run it back up to 6K RPM then into 3rd, run it up to 6K RPM then into drive, as soon as I put the car in Drive the RPMs will drop and refuse to go about 3K, and when I punch the gas pedal the car will not downshift into passing gear like it normally does.

I'm stumped. Please help.
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Orionsune
December 26, 2006.




I am going to answer my own problem for those who might experience the same problem.

It was my Throttle Position Sensor.

The strange part of this is, my check engine light came on, it took several weeks and it finally came on a few days ago, but when it did, and I had the codes read, it listed both the Throttle Position Sensor, and my MAP Sensor. I cleared the codes and continued to drive it as it was, and about 4 days the light came back on, so I had it read again, and this time it only listed the Throttle Positio Sensor, so I replaced it. Now the car drives like it never had a problem, and I am assuming the MAP sensor was getting strange readings since the TPS wasn't doing it's job.

All said and done, I believe the diagnostic software in this car must be un-reliable. I say that, because i've seen other cars where a sensor goes back and the car immediately displays the check engine light, it took my car several weeks of poor drive ability before it responded.
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Tiny
Orionsune
Jan 5, 2007.
Hi Orionsune--

Glad to hear you got it fixed and thanks for letting us know, hopefully it wll help someone else.

Tiny
Hyknrd
Jan 9, 2007.

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