I've owned 3 IROCS and 1 GTA in the last year and all were TPI. I know have an 87' IROC LG4 5-speed. I am getting both TPS(21) and VSS(24) codes and trying to fix. I measured the TPS voltage and it looks to be bad. It was 3.65 with ignition on with no throttle. So I think replacing it should do the trick. Now the VSS code I've never dealt with and would like to know if the TPS could be tripping this code? My speedo works perfect, and as I understand is cable driven, so could the VSS sensor on the T-5 need to be replaced? I figure I will not be able to tell until I correct the TPS but just wondering if there is any experience with this. I'm new to carbs and trying to learn, but I have TPI ingraved in the brain....
Any suggestions would be great.

Thanks and it's good to be back wrenching,

Tim

 

Which pins are you taking your measurements from? The readings should be taken from pin "A (negative)" and pin "B(positive)". If you are reading from pin "A" or "B" and pin "C", then you are reading the TPS signal to the ECM. If you are reading from pin "A" and "B", either your TPS is bad or your idle adjustment screw is out too far. Check position of throttle plates.

The Trickster!!!!!!!!!

 

I'm reading from the middle and bottom wire on the TPS plug. The idle of the car is great as is the drivability. I also need to mention that the SES light resets when I turn the car off and comes back on very shortly after starting or after a bit of driving. I've reset it and waited for the SES light to come back on and reads the same codes. The idle is high when first started and ten drops to normal, I figured that is the warm up cycle right? I reset it last night and drove for a while, but right before pulling into the driveway it reset the SES with same 21 and 24 codes.

Any suggestions?

thanks
Tim

 

Take your readings from the top and middle wires on the TPS.

The Trickster!!!!!!!!!!!!