91 sunbird, sensor problem

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Hi all. (Disclaimer: I know jack about cars)
I have a v6 automatic 1991 Pontiac Sunbird. It has been giving me all kinds of problems. It was working fine until i applied idiot power. I went too fast over a hill, got too much air, and hit hard. It started making a thumping like noise that got louder as i sped up. I took it to a mechanic and he replaced the axel cv joint on the front passenger side.

The noise stopped, but immediately after this i was driving down the highway and the rpms would rev way up and the car would lose momentum. The transmission appeared to be slipping. We decided to have the transmission fluid and filter changed. The mechanic said the filter didn't have excess metal, so the transmission wasn't falling apart, it just needed the fluid and filter changed.

(on a side note, it leaks oil now and the mechanic said the gaskets on the manifold need replaced) Immediately after having the fluid and filter changed, it started dieing when i put it into drive from a stop. Also it vibrates really loud as you come to a stop and then it dies. While rolling it we put it into gear and it went as long as we didn't make a complete stop.

A friend said this was from a sensor, but he lives too far away and i have no money for him to fix it. And I trust the mechanic i've taken it to about as far as i can throw him. Any input or advice would be much appreciated. Sorry for taking the last fifteen minutes of your life, but this car won't stop giving me crap.

posted by  Xander

The problem you describe (stalling when at a stop in gear) sounds like a Transaxle converter clutch switch problem....the lock-up function in your transmission is controlled by a switch and solenoid....what happens is the converter clutches "lock-up" at highway speeds creating a direct drive, almost like a manual tranmission. sometimes the lock-up solenoid or switch go bad and keep the converter clutches locked up...this will cause sky-rocketing temps in the converter, causing the clutches inside to "weld"(for lack of a better term) themselves together, this will cause the car to shutter and stall at stops while in gear.

A way to test this(or even a temporary fix) is to disconnect the converter clutch switch......it should be a blue or white 4-pin connector on the front side of the transmission(driver-side of engine bay, mounted low). This will cause the converter to not lock-up(only a few hundred rpm difference)at highway speeds and may cost your a little more in gas if you drive frequently on the high-way but it's much cheaper than the alternatives.

If, when you do this, the car stalls as soon as you put it in gear don't worry(yet). It'll most likely still stall because the clutches in the converter are still "welded" together. In order to get them to release, start the car in neutral or park rev it up and drop it into drive...it sounds half-assed but thats what they do in tranny shops. By doing that it should cause the clutches to break free from each other, if it doesn't work the first time...rev it up more and drop it into drive again. Then to verify that it's the switch or the solenoid, take the car for a test drive, get it up to about 50-60mph for a good 5-10 minutes then bring it home, it should no longer stall at stops. If it does continue to stall then your problem lies elsewhere, but it really sounds like that's the problem to me.

Get back with me and let me know what happens.

posted by  Sick88Tbird

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