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90 pontiac bonneville


tstokka's Avatar
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05-01-02, 08:55 AM   #1  
tstokka
90 pontiac bonneville

I've got a 90 bonneville with a 3.8L v6 auto-trans. When starting the rpms fluctuate from 1500 to 3000 and after a while it will calm down and run normally. the other day it just stalled on me and started right after. Any ideas what would cause the fluctuations. I pulled codes and got a 39 witch was transmission related, I think it was an old code.

 
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05-01-02, 09:17 AM   #2  
Joe_F
Could be a vacuum leak or carbon in the throttle body. Another possibility is a bad idle air control valve.

Clear the codes and re run the test and tell us what you have. Disconnect the battery for 10 minutes or so and then reconnect it and check for codes.

 
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05-10-02, 04:55 PM   #3  
tstokka
could this be two separate problems? 1, the code 39 came back again, tcc. I think this is causeing the rpms to fluctuate going down the road. 2, when I start the car it will run about 2000 and while its idleing rpm's jump all over the place

 
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05-10-02, 06:53 PM   #4  
Joe_F
It could. A TCC (Torque Converter Clutch) that sticks will feel like a stick shift car when you forget to depress the clutch out while decelerating. That is, it will buck and possibly stall out.

The "fix" is to disconnect the plug on the side of the tranny (external on some not on others) and it will be OK. You'll lose some fuel economy as a result. Some trannies have to be dismantled to get at the plug.

This car has a THM440T4 which I cannot recall if the plug is behind the side cover or not. Knuckles often recommends an additive for this which might alleviate the problem. I think Gunk or someone makes it. It's a band-aid solution at best.

The THM440T4 is nothing to write home about. Unfortunately a very lackluster transmission.

 
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