OK heres the deal,i have an 86 Trans Am 305 TPI.I have a brand new IAC valve(adjusted properly),a brand new EGR,Hpertech coil,cap and rotor,new wires,new plugs corectly gapped and a new airfilter.The TPS is the only thing i didnt buy new.

And heres the problem.When i start the car it idles fine then all the suddenly it starts to break up and then it idles high and stays there then comes back down and surges and it runs rough again.Sometimes it will even stall when it comes down from idle.And if i try to give it just a hair of gas to keep it from stalling,the rpms shoot up like i almost floored the gas.Someone told me to test the TPS and heres what i found.

Its adjusted to .54 volts.But it seems like it never stays there.i can adjust it to .54 and start the car and come back the the TPS volts are off then.And i know the screws arent loose cause i tighten em good.So i tried to get the WOT(Wide Open Throttle) reading of the TPS and the volts were jumping.Id slowly open the TB and watch the volts go up from the TPS and theyre fine until i get to around 3.5-3.8 volts...Once it gets to about there the volts dont stay steady and they keep jumping from around .36 volts all the way up to 40.27 volts.And i know its not really getting that many volts.BUt it wont keep a steady voltage reading once i hit that point until i go aways past that point in the volts.So its like theres a point between idle and WOT where the volts are messed up and jumping around really bad,all the way up to 40 some volts.

Im not getting any trouble codes at all or a ses light.Do you think the TPS is bad and the problem with my car running the way it is?

 

I would say for sure TPS is bad.
It must go from about .50v to about 4.0v VERY smoothly.

Good luck

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'91 Camaro 3.1 t-tops 44k original.
'98 GMC Sonoma excab 4.3 auto 35k.

 

The voltage should be .54VDC at idle and over 4.0 volts at WOT. The voltage should increase slowly and steadily relative to throttle position. if the voltage sticks, jumps, or falls the sensor may be failing and could be the cause of stumbling and other driveability problems I had a similar problem on 89 IROC 350TPI. I replaced the tps (adjusted it also), O2 sensor and it idles and runs fine now. I too did not get the SES light. I would replace the tps sensor if i were you. hope this helps. good luck!!

 

Well, there's no way possible with the engine not running, that you could measure 40 volts, in fact I don't think the alt is capable of going that crazy...but who knows...

Anyway, my suggestion is to borrow a different meter, and recheck the TPS again.

 

i really dont think its the meter,im thinking theres a short or something in the TPS causing me to get these weird reading and its weird cause i only get that weird problem when i get to a certain point on the TPS position.Im really thinking its the problem cause im thinking if the meter says the volts are jumpng high and low on and off like that,then it might explain my idle jumping high and low like that.I mean i know theres no way the TPS is really getting 40 volts but i dunno..lol...Ill try using another meter but i really think this might explain why my cars been running so funny.Maybe the TPS really is bad.

 

ok i tried another meter and its not that.Anyone?

 

Sounds like you need to replace it, end of story.

 

Mike has a very valid point, the readings of the TPS seldom goes over 4.00 volts IF the engine is not running. You need to test it with the engine running to find your max voltage.

Also, my voltage at idle is different at 0% TPS if my engine is running versus not running.