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2005 GT Random Stupidness

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dturchi

New member
So, I have a 2005 Grand Prix GT that will occasionally act stupid. One issue is that the transmission will shift funny similar to the known problems of the PCS and TCC solenoids. Check for transmission codes before turning the car off - NONE. Shut the car down, wait a few seconds. Problem gone.

I also have an occasionally random ignition miss. Noticable just off idle under light load. Check for any DTCs - NONE. Shut the car down, wait a few seconds. Problem gone.

I'm kind of wondering if I might have an issue with my PCM.
 


Have you done anything maintence wise to the car yet?

I know a dirty/bad MAF sensor can cause issue relating to the transmission.

Perhaps cleaning that and throttle body along with new spark plugs and wires may help the issue you are getting.
 
The car has had the plugs, wires, PCV, and air filter replaced. The throttle body has cleaned and the MAF replaced. When the car has the ignition misfire, all PIDs look normal. Which makes me believe the problem is either a CPS or the ICM. I'm not trying to suggest that I don't have a ignition or transmission problem. What concerns me is a lack of DTCs. My previous 2001 Grand Prix would throw a code if you sneezed or crossed your eyes. This car has some issues that I know should be throwing codes - but NADA. Makes it hard to diagnosis.
 
When you say the normal pcs and tcs problems. What are these normal problems that you are experiencing. I'm asking you to desribe them because around 03 the pcs should have been corrected and the TCS isn't really common. So I'm thinking maybe something else, like the other guys.

With more of a description, maybe we can narrow it down better.
 


At around 70 MPH under load like climbing a hill the transmission doesn't disenage the TCC as the throttle gets to 25%. If you press the throttle further, transmission will shutter (feels like the TCC finally disengages) followed by an immediate and harsh downshift into 3rd. At that point, the vehicle will continue to have harsh and delayed downshifts under load. Shutting off the car and restarting allows the transmission to smoothly operate the TCC without the harsh downshifting.

I can't really determine if the transmission is behaving this way because of a performance problem with the engine or the transmission is having issues. Some days the car is beast and other days, it drives like a tank. With the misfire or a max shift adapt I would expect a DTC. But have none.
 
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