[petem1957]

I have a '90' Chevy 350 TBI engine that is going to full throttle upon engine start up.

I unplugged the tps wiring plug but still the same problem.

Any ideas where to start troubleshooting?

[oldbogie]

Originally Posted by petem1957

I have a '90' Chevy 350 TBI engine that is going to full throttle upon engine start up.

I unplugged the tps wiring plug but still the same problem.

Any ideas where to start troubleshooting?

Check out the Idle Air Control (IAC). There is a stepper motor that contols idle air, it's going too far allowing to much air into the intake.

I would think there is a trouble code being set, does the "Check Engine" light come on?

Bogie

[Rob Keller]

Is the TRS Hooked up?
Throttle
Return
Spring

It was worth a shot.




R

[sbchevfreak]

Also, if you have manually opened the thottle (twisted the lever by hand), the sleeve that is over the cable end may have dropped down over the cable armour, and is holding the throttle open. The return spring on a TBI is wound around the shaft, in between the TBI and the throttle lever. I have also seen small rocks get stuck between the lever and the throttle stop, holding the throttle open.