Justen

So i'm not really sure what i should do about my idle problem. 90' TII, rebuilt the motor myself, streetport. I'm trying to get the idle steady, but i haven't had much luck. Floods and backfires on start-up. So naturally a bad TPS could very well be the culprit.



I checked the TPS with both a multimeter for resistance, and also with the 2-tester-light adjustment method... Failed the multimeter test, and i cant get the one tester light to come back on when i open and close the throttle plates after i adjust it.



I explained this to people on a number of forums and everyone seems to say that I definately need a new TPS, But then I hear from one of the guys at ROTARY-RESURRECTION that the multimeter test is not an accurate way of testing it. He said that he has seen TPS sensors that have passed the Multimeter test but performed like crap on a running car, and some that didnt pass and worked fine on runnning cars.



So what the hell should i do? New TPS's are pricey, i just want to know for sure that its the problem.

1988RedT2

Got any U-pull-it junkyards in your area? If so, a TPS shouldn't cost more than a few dollars. You might even get a good one.



Has the car run correctly since you put the engine back in it?

Justen

No its a fresh rebuild. It will idle, but very bouncy. And startup comes with much pedal feathering, flooding, and backfires. Because of all these problems, i haven't taken it out on the road to break the motor in yet.

89 Rag

If one (or several) of the input sensors are reading wrong, the ecu just fattens the fuel and retards the timing to reduce the possible damage. It always amazed me how putting a sensor in a bag on a bench that worked perfectly fine prior to removal, suddenly can't pass a test when re-assembeled.



Are you getting multiple codes, engine light on and/or blinking?

Justen

And thats precisely what i think happened... just had it sitting on a shelf till the motor went back in... worked fine before, but now its a problem. And what you said about the fuel/timing would definitely explain the fact that its flooding and that i can't get the timing set. I am running a walbro without a fuel pressure regulator, Could that cause a further flooding problem?



I am getting a few codes, but from what i can tell they seem to be emissions related, but i will double check those codes when i go home this weekend



I'll get back to you on what they actually are, thanks

89 Rag

Im not the one to ask about aftermarket fuel goodies, my car is pretty close to stock in that manner. The only change I made from stock other than some finesse motor work is upgrading the ECU, if you had a 20 year old computer at home, you'd probably shitcan it and get a new one too. The piggyback AFC wasn't a bad mod either.



I think a lot of this is covered in the FAQ section in one form or another though, grounding is HUGE, correct/working sensors, and the codes overlap sometimes meaning several systems will cause the same type of codes to appear.



Another thing I had to look at was the condition of the wiring and how they were kept while the car was apart, if they are left to drag the ground un-bundeled for an extended period of time varmits, pets, drunk friends can gnaw on the wiring causing all kinds of problems.

1988RedT2

If you are running a pump with a greater flow rate than stock, and it is completely unregulated, then yes, it will result in too much fuel.

Justen

I mean i just replaced the pump, it still goes through the stock s5 rail...



...but i dunno, would the stock rail and damper not regulate it enough?

CrimsonPride

If you're dealing with a rebuild and can't get the timing set, I would do the procedure for finding TDC and double check that the CAS is installed in correct position before buying more parts.



Also, I never had a bad TPS on any of my 2nd gens. Would they really give this bad a problem with startup and idle?



Maybe someone with a good running 2nd gen would be willing to go and disconnect their TPS to see how much it affects the startup and idle and report back the results?

CrimsonPride

I am starting to recollect, won't the cars startup and rev ok but not idle without TPS input. I know they won't drive well, but I mean just at standstill.