1990 2.0 Engine RPM verses Transmission shifting

[Paps]

1990 Pontiac Sunbird LE Convertible, 2.0 TBI with overdrive transmission has issues with transmission verses engine rpm. Engine has been completly overhauled, throttle body rebuilt with nos oem parts, and all engine and throttle body sensors replaced with oem nos parts. Engne does not idle consistantly but runs fine above idle. My worst issue is how the engine reacts when I shift from park to drive, reverse, or directly through to neutral. Transmission is a 5 speed automatic with overdrive. Engine rpm goes from a 400 /450 at idle to just under 1000 when shifting. What am I missing ? I've changed out the speed control and all external sensors I could locate near or around the transmission. These new parts are also nos oem components. Engines auto shifts up and down very well through MPH increasing and decreasing. Thanks for any and all suggestions.

 

[melsg5]

have you done a test of the throttle position sensor?

 

[bigclubs]

Pardon my spelling long day working outside.
I have a 91 convertable with the 2.0L 3 speed automatic and was having trouble with the vehicle at idle. After reading numerous articles suggesting there may be a vaccume leak, I finally found one about changing the Idle position sensor. It is located behind the throdle body. A real pain in the a** to get to the screws. Replaced the sensor and so far the car idles without stalling out. I was able to find the sensor on E-bay for $35. Most autoparts stores wanted $65. To check your sensor, remove the sensor, leave connected to harness, turn key to on (do not start) and see if the piston moves. Mine was frozen and not moving.

 

[Zimgxp]

Sounds like you are checking the Idle Air Control. The TPS should be on the opposite side of the Throttle cable.

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[DanSavage]

That's what he needs to check is the idle air control. it will send the idle to 1000 if it doesn't release when going into gear.