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Old 07-23-2010, 10:29 PM   #1
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TPS help

I've had my 97 wrangler now for about 6 months. In my opinion, it runs like crap. It's a 4 cyl.

Engine is real smooth, however, there is absolutely no power. I can barely get the thing above 55 on a slight incline.

With that being said, when I got the jeep, the check engine light was on. I was told that there was a bad TPS.

I went to replace my TPS and the TPS which autozone gave me didn't fit. I checked the model number and it definitely was made for a TJ. After a bit of searching, I realized that the TPS sensor which was compatible for MY jeep was a YJ sensor.

I'm not against the fact that someone might have dropped a 95 (or older) engine in the jeep. However, a 95 engine would use a 95 TPS sensor. So there shouldn't be a problem.

After dropping it off at the mechanic (who has spent hundreds of dollars of my money at this point), he has come up with the fact that when the gas is fully depressed, the throttle is only opening 50%. So this is why I'm getting a real lack of power. At 50% throttle, they are only open 25%.

He's suggesting that we get a new TPS harness so we can fit a 97 TPS back in (hoping that this will fix the issue).

My question is 2 fold:
1. Does anyone know where I can purchase such a harness?
2. Does anyone have any other ideas as to what might be wrong? It seems extremely odd to me (an the mechanic) that someone would have put a 97 engine in the jeep (if it was even replaced) but used a 95 harness and TPS sensor.

Any help would be greatly appreciated.

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Old 07-23-2010, 10:42 PM   #2
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Did you not get the memo about the new cover sheet for the TPS report? Ummm yeeaahhh.. I'll go ahead and get you that memo.

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Old 07-24-2010, 06:06 AM   #3
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So I wrote my statement above last night. I go to sleep and wake up hoping that there is going to be a great bunch of responses. I scroll down and see that someone actually responded....

I read the above statement and just start laughing. Huge thanks for the laugh!!!! I'm dead serious - very much needed.
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Old 07-24-2010, 06:50 AM   #4
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Is the butterfly on your throttlebody opening all the way? If it does not, the TPS is not your (only) problem. I had a similar problem with an 88 f-150. The butterfly was not completly opening. It was a bad throttle cable.

Hope this helps.
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Old 07-24-2010, 07:58 AM   #5
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Yes, the throttle body is opening all the way.
However, its only ready 50% when they are fully opened. This is what the mechanic is telling me. We know that theTPS is not correct for my year jeep. It just doesn't make sense that it was swapped out with a YJ. The harness isn't spliced. So, we can only assume that the engine was fully changed out (we don't really know). If the engine was changed out, then the TPS should be correct for that year. He is out of ideas though - so he wants to put my years/model sensor in and see what happens.
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Old 07-24-2010, 10:43 PM   #6
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Anyone else?
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Old 07-24-2010, 11:36 PM   #7
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Isn't the VIN stamped on the engine somewhere? Couldn't he see if the VIN on the engine matched the VIN stamped on the dash? That would tell you for sure if the engine has been swapped out...

I'm not sure what would happen if you swapped out the wiring and the TPS from yours with the wiring and TPS from a 97...might work. Just make sure if he does it, that he leaves enough wire to switch them back easily if it doesn't work.

What I'm wondering is...is it possible the previous owner swapped out throttle bodies from the 97 to a 95...maybe to port it or replace a badly ported one or something along those lines? That's where checking to confirm if the engine has been swapped or not would come in handy...if the VIN's match, then the engine has never been swapped and most likely the throttle body has been...or somehow someone switched the sensors and their wiring.
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Old 07-24-2010, 11:51 PM   #8
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Anyone know where the vin is located?
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Old 07-25-2010, 03:55 AM   #9
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The VIN is on all your paperwork... . title, registration, insurance card.

The TPS for a '97 is actually a '95. I had the same experience you did buying the wrong one. Seems '97's used some '95 parts. First year of TJ and tooling took a while to get up to speed. No one swapped your engine so don't mess around with wiring harnesses. . . unless you think there may be a break in the wire somewhere.

Now the TPS. I had a P0123 code, and two codes related to downstream O2 sensor, but had NO driveability issues. Did you measure the voltage at the TPS terminals as specified in the FSM?

I replaced the downstream O2 sensor and left the positive lead off the battery for 24 hours. I haven't seen any CEL or fault codes after almost 200 miles back on the road. YMMV

BTW, mine's a 4 popper and it runs great. . . has for the six years I've owned it.
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Old 07-25-2010, 06:05 AM   #10
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My 97 4cyl doesn't use the supposed correct part from autozone/advance etc., because the connector is different. But when I went to the dealer they pulled up the correct part with the correct connector. For some reasons it seems that early TJ's used the old TPS (or at least a different connector).
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Old 07-25-2010, 06:41 AM   #11
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It's a Chrysler thing. My 97 Ramvan is a mix of 95-97
parts. Always have to bring the part with me to match it up. You are going to have to troubleshoot the tps as per TJ2 post.
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Old 07-25-2010, 02:16 PM   #12
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Thanks for all the help guys.

As for the VIN number - I was asking where on the ENGINE I can find it. I know where to find it on the frame and registration.

As for the TPS sensor - I'm happy to hear that others have had a "fitment" issue with the 97 sensor and the YJ sensor. That leads me to believe that the sensor is correct - however - I'm still only receiving a signal for 50% when the throttle bodies are wide open.

Can someone tell me how to properly check the TPS with a volt meter?

Once again - I really appreciate all the help.

Oh yeah - I don't have any fault codes on my engine now. When I originally purchased the jeep, the engine light was on and it pointed to the TPS. The TPS was broken inside the harness and I had to spend a great deal of time getting the screws out and re-tapping. I assumed the reason why the original owner didn't replace it was because he couldn't get it out. Once I replaced the TPS (with the 95 TPS since its the only one which fit), the engine light has gone away and I haven't seen it on since.
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Old 07-25-2010, 05:56 PM   #13
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I am in your exact same boat. I have a 2002 TJ and the sensor I received from Autozone for a 02 didn't work, had to use an 03 TPS. My scanner reports the throttle only reaches 67% max. I then bought a VIN matched TPS from RockAuto and I have the same problem.

So far from my testing:
  • I can tell it isn't my throttle cable (this % happens even when I actuate throttle plate by hand with the cable disconnected).
  • It is also not the TPS connector OR wiring from the connector to the PCM. I have tested every pin from the TPS and traced it back to the PCM with perfect connectivity using a DVM. The ground pin also checks out. I think it may be safe to say replacing your TPS harness will do nothing but you'd have to do those tests in order to be sure.
  • My 5v reference voltage sits solid at 5.11 volts. This is something your mechanic should also check out, if this voltage is low you may have dirty ground points and it may be the source of your problem. I have a document that points out all of these points if you wish to dive into this yourself.
  • I took the sensor off of the TB for shits n giggles while it was still connected and checked its range on my scanner. It read from 4% to 98% when actuating it with a screwdriver. This tells me that the sensor is functioning correctly and the problem now lies in the TB and/or throttle plate.

I'm not sure if there is a way to adjust the flat flange that turns the TPS while you increase the throttle or not. I am waiting back from a Jeep service technician my father knows about this problem and will post my results. If you or your mechanic find anything about this PLEASE post it!
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Old 07-25-2010, 07:29 PM   #14
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genarro,

The VIN is NOT stamped on the engine. . . the build date is stamped on the block between cylinders 3 and 4.

Wisdom of the forum says that slop in the throttle plate assembly may cause problems. There was a big write up about how to and what brand of cleaner to use.

FSM says: "The TPS can be tested with a digital voltmeter. The center terminal of the TPS is the output terminal.

With the ignition key in the ON posititon, check the TPS output voltage at the center terminal wire of the connector. Check this at idle (throttle plate closed) and at Wide Open Throttle (WOT). At idle, TPS output voltage should must [sic] be greater than 200 millivolts. At WOT, TPS output voltage must be less than 4.8 volts. The output voltage should increase as the throttle plate is slowly opened. . . "

It's not rocket science. The TPS is a variable resistor. As mentioned above feed voltage from the PCM is 5 volts.

Is there any chance anyone got the thing in wrong? "The TPS must be installed so that it can be rotated a few degrees. (If the sensor will not rotate, install the sensor with the throttle shaft on the other side of the socket tangs). The TPS will be under slight tension when rotated."

Just grabbing at straws here.
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Old 07-25-2010, 08:37 PM   #15
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TJ2 - I'm gonna try your TPS test this week. Monday is tomorrow and well...work comes first. Just so you know - the post above you is from MikalCarbine - not me. It sounds like he has a VERY similar problem. I'm going to guess that my TPS is working correctly (yes its installed correctly). But, I do want to make sure its putting out the correct voltage.
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Old 07-25-2010, 08:41 PM   #16
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Ya, mine is installed correctly too, hard to do it wrong because the throttle plate won't turn if the sensor is on wrong. My voltage I am getting out of mine is 0.446 to 3.747 (idle to WOT), this is theoretically in spec but it seems the range is a little off. I am going to make a bet your WOT voltage will be between 3.4 and 3.6v gennaro

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