Runs better with TPS unplugged

[Rooster14]

Hi all, first post here, but I read the forums a ton. I have looked all over for a solution here, but nothing hit the mark. Any help you can offer would be appreciated.

First off, this is my first 80, 91 3-FE. I love it! Owned a 60 long ago, but that is not helping here.

I am getting a CODE 51 accompanied by low power (very low even for a 3-FE), especially on hills. As if I am pressing the gas and it is not delivering enough fuel.

The TPS was bad, so I replaced with a new Denso model (tested fine on install). Still the same. Fuel filter, fuel sock, replaced. Tested Air Flow meter, Idle control valve, EGR system, vacuum..... all good.

Here is the kicker..... if I un-plug the TPS and run it.... it preforms the same (or better) as when it is plugged.

I am guessing it is either a bad wire from TPS to ECU, or the ECU itself. Any other thoughts?

 

[jonheld]

Code 51 is telling you that the ECU isn't getting the correct signals from the TPS or the AC clutch circuit or the neutral start switch.

Since you replaced the TPS, I would suggest you check continuity from the aforementioned circuits back to the ECU.
Also, was the new TPS an OEM part or aftermarket?
Were you getting the same code before the TPS replacement?

More details needed.

 

[Rooster14]

Thanks for the rapid response! Here are the additional details you requested.

Yes, was throwing a 51 prior to changing TPS.
Yes, TPS is an OEM part.

Have not chased down any wiring yet. (Hoping to avoid that chore if I can).

Engine seems to shift fine and respond as it should with A/C on.

 

[sdpall]

I have some similar issues not loss of power but getting a check engine signal, mechanic said it was a temp sensor and I didn't know if an OEM part is a must or not. The other issue I'm now having my mechanic said that the front differental "Ham" is bad not sure how he figured that out without taking apart. Also can't find a ham how much should it be to rebuild or any suggestions were to get one. Thank you new to form but have had land cruisers for almost 20 yrs.

 

[kidglove13]

What is a front differential ham?

 

[Rwhat]

Did you use a ohm meter to adjust the resistance sweep on the TPS sensor according to the specs in the FSM.

 

[CruiseOrlando]

What is a front differential ham?

I think it might have to do with the swine that suggested it needed replacing...

 

[jonheld]

Thanks for the rapid response! Here are the additional details you requested.

Yes, was throwing a 51 prior to changing TPS.
Yes, TPS is an OEM part.

Have not chased down any wiring yet. (Hoping to avoid that chore if I can).

Engine seems to shift fine and respond as it should with A/C on.

So it's pretty safe to assume at this time you really need to check point to point. If you're getting the same code after swapping parts then you need to troubleshoot. No way around this.
I'd put money on the TPS harness.

 

[jonheld]

I have some similar issues not loss of power but getting a check engine signal, mechanic said it was a temp sensor and I didn't know if an OEM part is a must or not. The other issue I'm now having my mechanic said that the front differental "Ham" is bad not sure how he figured that out without taking apart. Also can't find a ham how much should it be to rebuild or any suggestions were to get one. Thank you new to form but have had land cruisers for almost 20 yrs.

You can read the codes yourself with a paper clip if it's OBD1. What's the code? What year is your truck? Is your diff ham smoked or honey glazed?

 

[CJF]

I have some similar issues not loss of power but getting a check engine signal, mechanic said it was a temp sensor and I didn't know if an OEM part is a must or not. The other issue I'm now having my mechanic said that the front differental "Ham" is bad not sure how he figured that out without taking apart. Also can't find a ham how much should it be to rebuild or any suggestions were to get one. Thank you new to form but have had land cruisers for almost 20 yrs.

Learn to use the search function, read all the sticky threads at the top of the page, and then post your own threads if necessarey, one topic at a time.

Don't hijack this one.

Welcome,

Curtis

 

[Rooster14]

Sorry for not checking back in sooner was on the river for a bit! Out of cell and laptop range.

I did use an Ohm meter to adjust the TPS per the FSM, and I agree that something is up with the wiring. I'll start running some continuity checks this week and post what I find.