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.

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. https://www.nopistons.com/forums/pub...R#>/tongue.gif



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

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.

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?

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

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.

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.

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?

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?

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.

Yea, I've tried this process a number of times...



"leading notch on the e-shaft pulley aligned with the metal pin sticking out of the front cover for TDC,

take out the CAS and align the two notches with the blind cap off of the CAS,

place the CAS back in assuring the notches dont dissalign... yadda yahhda"





If i'm doing this right, then can i just assume that the timing is correctly set?



..................................

and yes.... I am getting multiple codes,



and yes... the check engine light goes on and off every 5 seconds or so when it idles at anything lower than 1000 rpm, and very frequent bounces in idle as well

Ok, sounds like the CAS is in right. If you're really suspicious about the TPS, I think you should be able to monitor its output with the car running with a voltmeter at the EGI computer by backprobing the wire.

To answer your question, yes I think you can assume that its right or at least close enough that its not your problem.

okay good, that narrows it down a little

Alright, these are the codes its throwing:



9.....water temp sensor

25....solenoid valve (pressure regulator control (PRC))

31....solenoid valve (relief)

32....solenoid valve (switch)

34....solenoid valve (bypass air control (BAC))

42....duty solenoid (turbo boost pressure control)



now, given that i have all emissions/rats nest/idle control removed, is there anything else besides the water temp sensor that i should be worrying about? I also have electronic boost controller installed.

so it turns out, all i should really be worried about is the water temp sensor. everything else is normal for a new rebuild. Thanks for the advice er'body