Bad TPS?
 

86GT, HO 5.0EFI 5spd. Bone Stock except Hypertech Power Chip.

The idle is inconsistent, and cruising about 25mph, 2k RPM 2nd gear, the car has a mild surging motion. It seems to do this upon acceleration as well. If I accelerate hard from one stoplight, when I stop at the next the car idles at 1200 rpm for a short while, whereas it will usually idle between 500-800rpm.

The Cap, Rotor, Plugs, Plug Wires, Air Filter was all changed 6k miles ago.

Any help would be appreciated.

Thanks,

Jeremiah

You can check your tps voltage with a digital voltmeter. It should be around .95v at idle, and go to around 4.5v at WOT.

Your problem sounds kinda like a bad O2 sensor.

This may sound silly.....how do I check the TPS voltage? Does the car have to be running to check it? If the the voltage is off, is it adjustable or do I have to replace it? Where are the O2 sensors and how hard are they to replace?
Sorry for all the questions.

Thanks for the help, I am investing in a Repair Manual next week.

Jeremiah

I have the same car and the tps went bad after I got it wet. If you have a buddy with a stang just try his tps, it only takes a minute and a screw driver you will know in 5 min. if thats the problem.. Or if your local parts store as a good return policy you can do the same.. Good Luck.

By the way, what do you think of your Hypertech Chip????

Thats what this place is for:), your 02's would probaly have your check engine light on if bad, check the tps voltage bye putting some pins in the wires....dam forgot which ones, green and black? hopefully someone will correct me, im gonna go reset timing on my car so i will look at mine brb.

Do I check the TPS voltage when the car is running? Also, I don't think my 86 has a check engine light, if it does, I guess my o2 sensors are fine.

I bought the car less than 3mos ago and it had the Chip in it when I got it so I don't know the difference, my car is the only 5.0 I've driven. Seems to run pretty good.:)

Later,

Jeremiah

I remember just turning the key on, but leave motor off. black and green wires i think, i forgot to lookk, and i just got out from under my car.

Take a needle and pierce the green wire. Use that as the positive and use your throttle body as your ground. The voltage should read between .950-.999. Different people will tell you different settings for the TPS. Having a blown car I have found no difference between .950 and .995. To adjust, loosen the two screws holding the TPS and rotate slightly.