Hey guys,

I got this 85 Trans Am maybe a week ago. It ran perfect, the engine looks like new (305 TPI)

Now, It has a very high idle...Sometimes 2k RPM's...Still runs great at wide open throttle...but I have to apply the brakes so hard to get it to stop at light or where ever...

Then sometimes it will finally become low...but then it stumbles...Sometimes my engine light will come on...

Its all stock, no leaks, no smoke at any time...
Any idea's?

Thanks much for any imput!

Check your TPS, it should be at 0.54 at idle. A friend of mine with an 85 T/A had the same problem as you. It turns out his TPS was shot.

Thanks for the heads up...

How does one go about checking it?

Its runs great at wide open throttle, but way high idle usually...then sometimes it will go down...then it stumbles and acts like it might stall...
Thanks again!

Also check the MAF sensor,they are famous for causing that kind of nonsense.The conncections on it start going bad and it can drive you crazy with very intermittent problems(had mine do the same thing)try pulling and lifting up and down on the wires going into the maf sensor and see if it changes when you do that.

Buy a multimeter ($10- $20) and pop off the cover of the TPS and plug in the black tester in the hole where the black wire is and the red tester where the blue wire is. You'll have to turn the ignition on and you should get a reading of somewhere around 0.54. On the driver side of the throttle body at the back, there is a hole, that you can stick a torx screw bit into to adjust the TPS. If you try adjusting it to .54 and the car doesn't run that well and you can't really get it close to that, then your TPS is likely screwed. It'll probably cost around $30 for an aftermarket TPS.

You should check out this link for TPS & IAC adjustment procedures:

https://www.thirdgen.org/newdesign/tech/tpimod2.shtml