89 xj 4.0 auto TPS spec

Ulver44 · Jul 11, 2010

The previous owner said he replaced the TPS and TCM before he sold it to me, but that the TPS just needed to be calibrated. So with switch on I got 4.71V input and 4.6V output. Input never changed when adjusted, but output would change to 4.36V.

Output/Input does not give the optimum .825-.835 reading in any position. The TPS looks new. Am I doing this right?

The main problem I have is that it tries to stall/stumbles on takeoff. But also in the heat while driving, my brakes get hard like I'm losing the brake booster and it wants to cut off. Is that a vacuum leak at the booster or maybe vapor lock? Idle RPM varies during these instances.

It also seems to shift at a low RPM which sucks. Is that normal for these vehicles?

Thanks for any help!

joe_peters · Jul 11, 2010

On the four-wire connector to the TPS, you want output voltage to be 83 percent of reference voltage. That means 83 percent of 4.71 volts, or 3.91 rounded. If you can't achieve that, replace the TPS. Note: both screw holes in the TPS are slotted, have you taken advantage of all adjustment possible?

Check your vacuum system--is the vacuum reservoir still present--behind the front bumper, passenger's side? Vacuum lines around the battery like to break. What transfer case? If you have the NP231, 2wd/4hi/N/4lo then you have a vacuum disconnect D30 CAD axle in the front and its vacuum fittings/motor/lines could be leaking. Vacuum leaks will effect the booster to some degree.

What is the transmission switch set to? Power or Comfort? What is the condition of the transmission fluid--color, smell, quantity? Have you adjusted the throttle body pressure cable? We know the TPS isn't right.

Ulver44 · Jul 11, 2010

I swung the TPS all the way and those were my results, so I'll get a new TPS. I hope the one's auto zone carries aren't junk.

I still have the vacuum reservoir behind the front bumper and I do have a vacuum disconnect D30. The problem is only intermittent, but next time it happens I will check the places you mentioned. Didn't know about under the battery.

The transmission switch is set to Power. The fluid smells a little burnt but I've been told not to change fluid on an old trans if it isn't causing you any problems. I don't know about the throttle body pressure cable. Should I adjust it?

joe_peters said:
On the four-wire connector to the TPS, you want output voltage to be 83 percent of reference voltage. That means 83 percent of 4.71 volts, or 3.91 rounded. If you can't achieve that, replace the TPS. Note: both screw holes in the TPS are slotted, have you taken advantage of all adjustment possible?

Check your vacuum system--is the vacuum reservoir still present--behind the front bumper, passenger's side? Vacuum lines around the battery like to break. What transfer case? If you have the NP231, 2wd/4hi/N/4lo then you have a vacuum disconnect D30 CAD axle in the front and its vacuum fittings/motor/lines could be leaking. Vacuum leaks will effect the booster to some degree.

What is the transmission switch set to? Power or Comfort? What is the condition of the transmission fluid--color, smell, quantity? Have you adjusted the throttle body pressure cable? We know the TPS isn't right.

joe_peters · Jul 11, 2010

Throttle pressure cable adjustment link: http://naxja.org/forum/showthread.php?t=1015963

Renix sensor link (book mark this one): http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Aw yes, the URBAN LEGEND THAT REFUSES TO DIE! Ok, quick and dirty--the ONLY thing that allows an automatic transmission/transaxle to work is the FLUID. The fluid MUST be changed. Anyone telling you anything else is ignorant, a liar, or a fool.

Do a search for "poor man's flush". Change the fluid.

cruiser54 · Jul 11, 2010

joe_peters said:
Throttle pressure cable adjustment link: http://naxja.org/forum/showthread.php?t=1015963

Renix sensor link (book mark this one): http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Aw yes, the URBAN LEGEND THAT REFUSES TO DIE! Ok, quick and dirty--the ONLY thing that allows an automatic transmission/transaxle to work is the FLUID. The fluid MUST be changed. Anyone telling you anything else is ignorant, a liar, or a fool.

Do a search for "poor man's flush". Change the fluid.

Joe is correct. I choose to call those suggestions "old wives' tales" instead of urban legends, but they're the same thing: BS repeated often enough that they're taken for the truth.............

Ulver44 · Jul 12, 2010

Ok, I'll change the fluid. I did the Throttle pressure cable adjustment and it's a bit more responsive now. It didn't stumble during the test drive but that doesn't always happen so I'm sure it will come back. Will get a new TPS when I get paid.

I'll look at the sensor link tomorrow. Thanks again!

joe_peters said:
Throttle pressure cable adjustment link: http://naxja.org/forum/showthread.php?t=1015963

Renix sensor link (book mark this one): http://www.lunghd.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Aw yes, the URBAN LEGEND THAT REFUSES TO DIE! Ok, quick and dirty--the ONLY thing that allows an automatic transmission/transaxle to work is the FLUID. The fluid MUST be changed. Anyone telling you anything else is ignorant, a liar, or a fool.

Do a search for "poor man's flush". Change the fluid.

89 xj 4.0 auto TPS spec

Ulver44

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joe_peters

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Ulver44

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joe_peters

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cruiser54

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Ulver44

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