Recently bought 91 GTA

Plugs were undergapped at .030 but not old. I put new ones in anyway. Replaced the O2 sensor. Cap and rotor replaced. They all looked old. The cap and rotor were horrible. Can't see how it ran as good as it did.

Changed the TPS. It measured .64 and was not adjustable. No idea where that came from. Lucky I had a spare and put that on adjusting it to .54. Cleaned the IAC and reassembled, took apart the whole TB actually. All whistling clean now! New fuel filter.

Thermostat was stuck open. Replaced that and now it's running at the right temp.

Still have to throw on the new plug wires.

Will have to recheck the timing. It was 6BTC before I done any of this.

It passed emissions before I did all that. It had horrible milleage, now it's much better. Was getting under 14 mpg combined city hwy. Now I can get over 23 mpg if I stay out of it some of the time.

 

The TPS was probably just fine. The TPI installations with a fixed TPS would sense the TPS voltage when the ECM powered up, and presumed that to be the closed throttle position. As long as the voltage was under something like 0.90 VDC at the closed position, the system would work fine.

 

SD only thing? I'm only starting to look at it abit closer now since I have one.

 

With the speed density system they went to a fixed TPS sensor that you cannot adjust. With the MAF systems the TPS sensor was adjustable. You can interchange them. However in my opinion the adjustable one is best and cheaper. Go figure.