C/E and Surging

[Beatjeep]

I tried searching for my symptoms but couldnt come up with an exact solution so I decided to post...

I picked up a 97 XJ 2 door for 500 bucks from a neighbor. The thing ran fine when I first got it. I took it through some trails with puddles and a little after that I got a C/E light. I got it checked at autozone and it said that the TPS is faulty or shorted out etc etc. Well I took the TPS off of a 93 4.0L ZJ and it connected fine but the same problem occurs...While pressing the throttle anymore than slight pressure, the engine seems to cut off completely then kick back in and cut off, almost as if something is stopping gas from getting to the engine. Also on startup it revs quite high, around anywhere from 1200-2000.

Should I go and buy a new TPS (Id rather not waste the 53 bucks) or do you believe there are other problems at stake here?

[Beatjeep]

Update:

I just went for a test drive with the TPS unplugged...it idled absolutely fine so it cured the bad idle however the surging/bucking when accelerating problem still occured...any ideas?

[XJ4PLAY]

I believe there is a reset procedure to follow after replacing the TPS. Did you follow that?

[Beatjeep]

:confused1 Is the procedure simply resetting unplugging the battery for 15 mins?

Otherwise I am not aware of any reset procedure??:confused1

[Rick Anderson]

There may a difference between a '93 and '97 TPS. Most Chrysler, and others, switched computers over in '96 from the switch to OBDII from OBDI, requiring all new computers. Not sure on XJ's since they are classified as trucks they probably weren't required to make the swap over.

You can check a TPS with an OHM meter, it should steadily change resistance as its turned. There is a closed and open range of resistance that it should meet, but the biggest point of failure is that they don't steadily change resistance as they move, they jump up and down and all over in resistance as you turn them.

As well, on most vehicles its easy to incorrectly install a TPS, they are suppossed to be indexed to the blade on the end of the shaft, its easy to put them on knobs of the TPS on the wrong sides of the blade on the end of the shaft of the Throttle Body.

Haven't done this on an XJ, this is my experience with other vehicles, so it could be partially or completely wrong, but its somewhere to start.

[lawsoncl]

There may a difference between a '93 and '97 TPS.

Looking at chryslerpartsdirect.com and napaonline.com, I get different part numbers for the TPS on a 93 ZJ versus a 97XJ. The 97XJ TPS is more expensive too.

The 00 XJ FSM, says the sensor output voltage should swing from about 0.26 at idle to 4.9 volts at wide open throttle. This is nearly identical to the voltage swing specified in my 93 Jeep FSM, which would say the sensor is probably the same? I guess the easy way to check this is to get out the meter and measure the voltage at the sensor at closed and full-open throttle (key-on, engine off). Make sure it changes smoothly as you move the throttle (an analog meter is really nice for this). I'm betting you need to get the correct sensor.

Guess you discovered that the TPS sensor really doesn't like getting wet. :} I have heard of someone drilling a small hole in the case and flushing it out with contact cleaner.