3FE Error Code 51 Help

[Jrock]

Hope someone can point me in the right direction with the summary i am about to give.

Overheated my 3FE. Bought a used motor to swap in. Did the swap myself in my driveway. New to me motor fired right up. It seems to idle fine IMO. However it has a 51 error code and accelerates at about 1/2 to 1/3 the speed of my old 3FE. I pulled the throttle body and checked the TPS and it was within range. Just for giggles i took the TPS off of my old motor (which was working fine) and installed it and adjusted per FSM specs that i found here on Mud. Still same code and wont accelerate. Really feels like its running on 4 cylinders.

I wondered if it might be a wire problem so i checked connections at the ECU and then cracked open the harness at the firewall just inside the engine bay. Checked wires for continuity (spelling?) from there to the connector at the TPS. No broken wires.

Where do i go from here? I feel lost.

Now the bad news.....its a 91'...STOP...put down the shovels and pitch forks...dont force me back into the 80 series section

I was told i would find more on 3FEs here than in the 80's section.

I have searched and read many threads but most seem to adjust or replace the TPS with luck. I am having no such luck. Thanks in advance for any help.

 

[Land Speeder]

I spoke with Jason for a bit on Saturday about this and agreed with him the TPS mainly for the code it's throwing as well as the characteristic of it not accelerating correctly.
The new-to-Jason engine came out of Cattywampus. It ran fine until the day Catty got parted out. Never a code, whimper, nuttin'.

 

[slcfj62]

Here is a thread I started awhile ago. It has some great troubleshooting links. Pablocruise had an awful time before he got his TPS problem resolved.

https://forum.ih8mud.com/60-series-wagons/325371-3fe-efi-primer-knowledge-pool.html

 

[Jrock]

*UPDATE*

Changed my ECU with the one that was in the doner truck. Instantly better on start up. Idle was high but i could already tell it was smoother. And now no code 51. However, when i put it in drive RPMs dropped to about 400-500 and it was a little rougher. Still had no acceleration and the code 51 came back.

I loosened the TPS with the old ECU in and turned the TPS back and forth and noticed no change in the motor. With the doner ECU in i did the same and the motor would idle up and down.

The latter is what is supposed to happen correct?

 

[slcfj62]

It will idle high until it warms up, but yes, it sounds like the donor ECU is working.

 

[viking cruiser]

I just went through this problem and it was the TPS get an ohmmeter and check it according to the FSM made mine better right a away.

 

[Jrock]

just finished setting my TPS according to the FSM. Motor seems like its running great in park or neutral. When it is put into gear is when the rpms drop way down and it has no power. It is idling high right now..about 1000-1200 but when put into gear it drops to about 500.

Best way to describe the feeling i get when pressing the gas is: when driving a 5 speed and you try to shift into 3rd gear but hit 5th instead. That is how it feels from the start.

Starting to wonder if something pulled loose on tranny when i lowered it to reach top 2 bell housing bolts

 

[terryjmatthew]

You ever get this figured out? Sorry you had trouble with it.

 

[jimmykickstand]

Yes that is my problem to a T....any fix?

 

[l1coeea9]

Hope someone can point me in the right direction with the summary i am about to give.

Overheated my 3FE. Bought a used motor to swap in. Did the swap myself in my driveway. New to me motor fired right up. It seems to idle fine IMO. However it has a 51 error code and accelerates at about 1/2 to 1/3 the speed of my old 3FE. I pulled the throttle body and checked the TPS and it was within range. Just for giggles i took the TPS off of my old motor (which was working fine) and installed it and adjusted per FSM specs that i found here on Mud. Still same code and wont accelerate. Really feels like its running on 4 cylinders.

I wondered if it might be a wire problem so i checked connections at the ECU and then cracked open the harness at the firewall just inside the engine bay. Checked wires for continuity (spelling?) from there to the connector at the TPS. No broken wires.

Where do i go from here? I feel lost.

Now the bad news.....its a 91'...STOP...put down the shovels and pitch forks...dont force me back into the 80 series section

I was told i would find more on 3FEs here than in the 80's section.

I have searched and read many threads but most seem to adjust or replace the TPS with luck. I am having no such luck. Thanks in advance for any help.

Ask Jonheld, the 80 series 3FE guru.........

 

[STICKP]

Ever get this sorted out? I'm having the same trouble right now.

 

[paulelliott]

Bringing this back as I'm having the problem as well in my 91 FJ80. Saw there were two others having the same. Very curious ...

 

[bigred450]

any update? my 92 has this problem

 

[LandCruiserNut]

any update? my 92 has this problem

I second for an update. My 92 now has a code 51