what are the symptoms of a bad tps? car is hard to start and will die if the pedal isnt held down slightly could this be a bad tps?

It could be several different things. In my experience when my TPS went out I had a problem with the car bucking and surging while cruising down the highway. I think if your having problems just with the idle that I would look for vacuum leaks or even a bad IAC valve.

iac is new well like 3 months old some new vac lines i was told it may help the car start quicker but not by a mechanic

A bad tps will cause you to get bad gas miliage, run very lean, or so rich to the point that the car will backfire. It will also cause the car to jump from 2000 and drop to 500 rpm at idle. It will surge and it sucks, fortunately for us GM used a sensor that is primarily plug and play. Get one anyways, chances are that it is bad and they are only about $60 at Autozone. You can also change it yourself in about 5 minutes....

NOTE... do not touch the idle air control screw....this is bad....

Kyle

Korupt,
The TPS is a potentiometer. The voltage that it sends back to the ECM will regulate the gas entering your combustion chamber. The actual position of your gas pedal under different vacuum conditions will indicate dwell time and fuel delivery at the injectors. A ratcheting action during acceleration would be one symptom.
It's easy enought to install a TPS, but not without setting the minimum air rate with the IAC and proper voltage at idle and WOT of the TPS. Without these adjustments the tPS replacement is worthless. So be sure to do it. So yes the TPS could very well be your culprit with the symptoms you describe possibly because of the initial voltage setting at idle (about .54 v.)
You mentioned that the IAC is recent? That also has an initial adjustment on installation. When you replace the IAC, it is also important that you clean the plunger port thoroughly in the casting. Otherwise the carbon blockage of the air passages can cause improper idle (smoothness and rpm's).

May be the TPS but it sounds like the idle air passages are plugged. Try squirting some carb/injector cleaner into the ports on top of the TBI; not down the barrel but into the two openings on opposite sides of the barrel top. That's where the idle air enters that bypasses the throttle plate.

My bet is on the IAC or something associated (wiring or air passages) - I was messing with my car, and after a ECM reset (pull the power for 10 sec), I accidentaly had the gas down a bit when I started it. It "learned" the idle where it was with my foot on the gas and it refused to stay lit unless I kept my foot on it. Oops. Sounds exactly like your symptoms though - make sure the IAC is alright (might have to adjust the pintle? I wouldn't try it unless you're outta options), wiring is alright, make sure the idle speed screw on the TB is set at a reasonable place, then reset your ECM and see if it'll start and run ok. Good Luck.

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Chris

Blue 1987 GT Getrag 5 speed, 1" lowering springs, 225 50R16 rims and tires, Fiero Store 9 3/4" HD clutch
Silver 1986 2m4 THM 125c automatic
Black 1985 2m4 SE Isuzu 5 speed (no paperwork)

the car hasnt had any problems for awhile but before i take it on the road i would like to replace the tps, o2 sensor and the gasket going from the tb to the air cleaner thing should this help calm down the idle/ stopp it from stalling

when i had a high idle on my 86 gt i replaced the map sensor, coolant temp. sensor, and checked all vacuum lines. it was the darn tps... soon as i replaced it that took care of the 1700 rmp idle..

welcome and good luck..

pc..

mine idles around 2000 when i first start then it calms down to a little about 1000 but after a while it calms down. im 16 and cant afford to put insurance on the car just to have it be unreliable again so i think im gonna replace the crank sensor,tps,o2 sensor and the gasket from the throttle body to the air cleaner just to be safe.

quote Originally posted by PCGamer: when i had a high idle on my 86 gt i replaced the map sensor, coolant temp. sensor, and checked all vacuum lines. it was the darn tps... soon as i replaced it that took care of the 1700 rmp idle.. welcome and good luck.. pc..

9 times out of 10 a fast idle = a cracked/ rusted EGR tube, which creates a vacuum leak.
To test it, Remove the air intake hose, hold the throttle wide open (not running) and spray half a can of carb cleaner into thr intake. If you see a wet spot anywhere on the EGR tube, theres your problem.

Idling at 2000 for the first maybe 5 minutes is normal, so long as the idle drops to the "normal" 1000 is. It is caused by the car being in "open loop" and the O2 sensor needs to heated and other conditions met until the computer will enter into "closed loop."

the idle doesnt usually drop until i rev the engine once then it drops down i dont know if this is heating it or whatever but like i said i want to make the car as reliable as possible, i am testing to fuel pressure tomorrow but i am definatley getting the gasket and the o2 sensor