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Speedo, cruise control, and delayed shift issue

Bigred69

Bigred69

New member
I have what seems to be a speed sensor issue with my 2000 Grand Prix GT, but here's the kicker! I have tried 4 separate speed sensors that I know were good, with no improvement. The wiring is good. I have checked and rechecked. It sets no codes. Weird thing is when it's really cold it works flawlessly. Cruise works, speedo, trans, everything until it warms up. Can ATF expanding with increase in temp. Cause a distortion with the speed sensor and reluctor? I will be dropping the pan for service and inspection tomorrow. Let me hear some ideas. Also any recommendation for ATF? 160k miles on car. Thanks guys!
 
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Standard Dexron 3 is the fluid for that year car, any brand will do.


Have you tried cleaning the MAF sensor?? I know that if its super dirty it can affect how the car shifts and drives.

Though it seems you have more than 1 issue here as 3 different things are affected. It's kinda hard to guess at what all is going on.
 
MAF is brand new. All the systems affected are reliant on the speed sensor. But no codes. And the fact that temperature directly correlates with drivability has got me stumped.
 
Speedo reads slower than actual speed.The faster you go and the warmer the car gets, the farther off and more "bouncy" the needle becomes. Because of this erratic speed the cruise freaks out trying to compensate. Trying to stay. at a steady 50mph while speedo bounces makes the car surge.
 


I'm thinking a little differently. Speedo is going to affect shifting etc. Pull the VSS sensor and clean the metal fragments off it. If there's anything more than a paste on it.. take pics.
 
I'll pull the vss and take pics tonight. Only thing is I've done that before with no improvement. I've tried 4 different speed sensors that were all tested in another car and known to be good. Is it possible for the reluctor to develop some kind of shimmy? They are pressed on aren't they?
 
Ok.. sorry, forgot what you had posted. Skip the pulling of the sensor then. That would be a waste of your time. The reluctors are pressed on and IIRC Drunkie had found a link at one point that linked some trans shifting issues to the reluctor swelling and giving bad readings.
 
I thought I had read an article about that awhile ago... The wife just bought a new car and I have my bronco so maybe its time I gave the Pontiac a serious overhaul and maybe bump the power up a couple notches...
 


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