Computer doesnt read TPS.....

[SleeperMark]

I searched for hours on this. A few months back I had a hanging idle problem and fixed it with a new TPS. after a month and a half it went out again, exact same thing. After replacing it a second time I noticed that my problems with a slight miss when cold and when i rev the engine as the rpm's fall they hang around 1,500 or so for about 3 seconds before falling back to 700. So, I took her down to the performance shop and had a diagnostic ran. O2 sensors: Open, Fuel: Rich, everything else normal except for the TPS reading. It was at .87V at closed and .87V again at open....... pulled it off and did a sweep test and it was fine... So I assume the computer is not seeing the TPS and/or there is a short somewhere. Any ideas????

1995 Mark VIII. 2.5in borla pro xs with an H pipe no 3rd cat other 2 are stock. 167,000 miles. New plugs, wires, cam position sensor, and checked coil packs for spark and they're fine. I run 93 Octane all the time from Ayerco. Same problems with 91 V power from shell.

 

[SleeperMark]

Also. codes...

412: Cannot control RPM during KOER high RPM check
336: EGR sensor circut voltage higher than expected
538: Insufficient RPM change during KOER dynamic response test

 

[chris2523]

412 sounds like a stuck idle air control valve. common problem on these cars.
336 is probably a bad/stuck EGR valve.
538 just means you didn't enter the cylinder balance the cylinder balance test probably. this is because your tps isn't working. you have to stomp the gas pedal after a KOER to enter the cylinder balance test.

sounds like your intake is pretty gunked up. buy new gaskets and some carb cleaner and clean that sucker out.

 

[SleeperMark]

Well the IAC is about 5 month old. Had both upper and lower intake manifolds dipped and cleaned and replaced gaskets for both. EGR probably is stuck but it would be doing the intake a favor anyway.. Thinking maybe a seafoam treatment? ive heard both good stories and horror stories........

 

[SleeperMark]

The only big thing im worried about is why i dont have a TPS reading. Does anyone know where the wires rout? maybe I have a short somewhere, that would explain why theyre going bad..

 

[Sapperfire]

Sounds like another bad TPS to me, what brand are you using?

 

[SleeperMark]

motorcraft went out, replaced with BDW, that went out, now its a duralast

 

[Sapperfire]

Check the blocks ground cables

Also check for moisture around the connector or any other wiring issues

 

[NetKeym]

Here is the way to troubleshoot (I know the diagram is for a different engine, but it has the same pin-out & color codes for the TPS):

1) Test the TPS itself with an ohmmeter and make sure it sweeps; you said you already did this.
2) Unplug your ECM under the dash, hook your ohmmeter between pin 26 (Circuit 351 - BR/W) Reference and pin 47 (Circuit 355 - GY/W) TPS while you depress your accelerator.

If your ohmeter doesn't sweep the same way on test 2 as it did test 1, there is a problem with the wiring between the ECM and TPS.

 

[chris2523]

(I know the diagram is for a different engine,)

mmmmm, supercoupe/xr7.
neat picture.

 

[SleeperMark]

well, computer is reading tps fine.... cleaned ground on block (it is a BIT*&) and all other grounds. Still have the same problem. Gunna try to take the duralast back and just get a motorcraft. If not ill do coil packs.