TPS only reads 9%-85%, off-idle bog, poor throttle response


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Jan 20, 2018
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Hi everyone.

I've got a 2004 Alero that has been having some issues with fuel economy and off-idle bog. Also, weak engine braking and rev hang when driving aggressively. I plugged my code reader into it and noticed that with the butterfly closed the TPS reads 9%, and at WOT it will only reach 85%.

I've never seen a TPS fail in this particular way though so if anyone can confirm that their throttle position ranges from 0-100% then I will replace the TPS. Also, shouldn't there be a calibration routine to reset that 9% to 0%? I have tried disconnecting and reconnecting the TPS but it does not recalibrate automatically.

This is probably quite serious for an Alero as it has no MAF and has to calculate the mixture based on RPM and TPS, right?

If I stomp my gas pedal from idle in neutral the motor will bog for 1/2 second and then it will rev. Also the top end throttle response is crap. The butterfly does open fully but I suspect the mixture is way off if it's using 85% to calculate the fuel.