Ok, I went searching on this site for my answer, but couldn't seem to find it. I noticed that some cars have the adjustable TPS and some have the non-adjustable one. My 91 Firebird has the non-adjustable TPS. So here's my question, if it's out of spec, do I just have to replace it with a new one? I can't adjust it?

 

Brian

The later ECM's (like yours) have ability to deal with wider range of TPS values and the older slotted TPS sensor mounts are no longer required. What is your TPS voltage at idle and WOT? Generally speaking, according to FSM, at idle 0.2 to 0.95 Volts is acceptable and TPS voltage should increase at a steady, linear rate until WOT is achieved. At WOT 5.0 volts (give or take) should be the norm.

You can check your TPS voltages with DVM by probing pin C of the TPS connector (dark blue wire).

//RF

 

Voltage at idle is right at 0.54 volts and WOT is around 4.6 volts.. All seems to be right within spec. This rough idling and surging is really starting to bug me.. Only surges at idle too, doesn't do it when I'm giving it gas or maintaining a certain rpm above 1k-1.5k. I've been noticing a gas smell lately too while I've been working on the car. Thinking I should probably check the fuel pressure regulator next.

 

did you ever find your problem

 

Well, I found my problem with the surging.. That just took replacing my TPS and IAC valve and adjusting it.

Unfortunately I haven't figured out my rough idle problem yet. My car actually idles a little smoother in drive than it does in park. Still trying to figure out why that is.
I'm getting ready to put a new exhaust on and smog my car, so we'll see if this rough idle is actually a slight miss or what. I'm thinking if the car is missing, I should fail my emissions test pretty horribly.. We'll see though..

I guess I should add that other than the roughness, the car runs great. Doesn't smoke or burn any oil, has lots of power (for a 305). Also just recently drove it on a 200 mile trip and it did great. That's why I don't really think it's anything too serious. Just more of an annoyance than anything else.

 

My non adjustable TPS when new was .55 at 0% and 4.5v at 100%.