FJ62 TPS Help

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Dryfly43

Dryfly43

10 Year
Joined
Dec 18, 2011
Threads
20
Messages
94
Location
Andalusia, AL
HELP!!! FJ62 (3F-E) TPS adjustment question:

Problem: old TPS tested out of spec, and running rich. Removed and found TPS would not return to home position under its own spring tension.

Solution: replaced TPS and adjusted on the bench with throttle body removed, with feeler gauges per factory spec.

New problem: Engine will barely rev off-idle under no-load condition. Falls flat on its face around 800-1000 rpm's.
Should I re-adjust TPS while the engine is running to try and fix this condition?


Did I do something wrong?

Very frustrating
Any help appreciated!!
 
Not sure I have the answer, but maybe a few questions that can help diagnose.

How long have you had the truck? Could PO have made some other changes to compensate for the bad TPS?

My thoughts is they may have changed something (ex: timing) to compensate for the TPS. Now that it is functioning correctly, it may have thrown everything else out of whack.
 
Beams37 said:
Not sure I have the answer, but maybe a few questions that can help diagnose.

How long have you had the truck? Could PO have made some other changes to compensate for the bad TPS?

My thoughts is they may have changed something (ex: timing) to compensate for the TPS. Now that it is functioning correctly, it may have thrown everything else out of whack.
Click to expand...
 
I have done the mechanical work on OP's truck. Came to me with compression leaking into the coolant. I replaced head gasket and put it all back together.... distributor has been replaced and reset base timing, plus TPS reset to factory spec. I set the TPS with feeler gauges between the stop screw and TB linkage arm. There is not a ton of adjustment there, but I set it just perfect according to FSM. The old TPS would let the engine rev...it was running super rich, but at least it would rev. As soon as we replaced it....very little throttle response. I even put the old one back on....same scenario. I am trying to figure out what the heck we could have done to mess this up! Makes no sense to me.
 
Check the resistance between the IDL and E2 pins on the TPS. It should be short/low resistance at idle, and open circuit when the throttle is open. If the IDL > Ground circuit is closed when you try to throttle up, a ~1100 RPM rev-limiter will engage.
 
Lead Head said:
Check the resistance between the IDL and E2 pins on the TPS. It should be short/low resistance at idle, and open circuit when the throttle is open. If the IDL > Ground circuit is closed when you try to throttle up, a ~1100 RPM rev-limiter will engage.
Click to expand...
I will do that. I set it that way before re-installing, but maybe it changed once the mechanical connections were made.

Thank you for the tip!
 
Lead Head said:
Check the resistance between the IDL and E2 pins on the TPS. It should be short/low resistance at idle, and open circuit when the throttle is open. If the IDL > Ground circuit is closed when you try to throttle up, a ~1100 RPM rev-limiter will engage.
Click to expand...
Ok ,so I verified continuity IDL-E2 at throttle closed position. It was still good from initial setup..

Here's the other thing that may have me confused:

Random misfires/running rough and rich at idle.

Inductive clamp on coil wire verifies random missing spark. When attempting to advance throttle, spark almost completely quits...big gaps between sparks.

Verified good waveform from distributor to ecm, and ecm output to ignition module (at least it's consistent/no gaps). Changed ignition coil, and checked voltage supply to igniter, static and loaded.

Note: Igniter gets too hot to touch after 30 seconds or so. Is this normal?

Also checked primary ignition waveform best I could, using a 10x probe on my oscilloscope to the - side of the coil. Truth is, I am not confident in my ability to read this waveform.

Could the ignition problem be misleading me on the TPS?

Once again...thanks to the group for any guidance!
 
WrenchMagnate said:
Ok ,so I verified continuity IDL-E2 at throttle closed position. It was still good from initial setup..
Click to expand...
Did you verify IDL-E2 opens up when you crack the throttle?

Note: Igniter gets too hot to touch after 30 seconds or so. Is this normal?

Also checked primary ignition waveform best I could, using a 10x probe on my oscilloscope to the - side of the coil. Truth is, I am not confident in my ability to read this waveform.

Could the ignition problem be misleading me on the TPS?

Once again...thanks to the group for any guidance!
Click to expand...
The igniter gets hot, but I don't think it should be that hot, that fast. Any possible way the coil primary wire is shorted somehow?
 
Lead Head said:
Did you verify IDL-E2 opens up when you crack the throttle?


The igniter gets hot, but I don't think it should be that hot, that fast. Any possible way the coil primary wire is shorted somehow?
Click to expand...
Yes, sorry... circuit opens when I crack the throttle.

I had previously replaced the coil, and I even re-installed the old coil today in case the new one was faut. No change.
 
have you looked inside the distributor cap?
is it rusty?
 
RodrigzCrzr said:
Im having the same problem. bogging while in drive. idles and revs up good in park and nuetral.!
Click to expand...
The one I'm working on won't even rev in park!

Have you checked your fuel rail pressure? Buy a cheap harbor freight kit and tap in at the cold start injector.
 
WrenchMagnate said:
The one I'm working on won't even rev in park!

Have you checked your fuel rail pressure? Buy a cheap harbor freight kit and tap in at the cold start injector.
Click to expand...
Mine has the same problem what your new problem developed.
but I will check the pressure since I have one.
Thanks
 
Last edited:
WrenchMagnate said:
.... distributor has been replaced and reset base timing,
Click to expand...

I think you need to recheck the timing to make sure that the distributor is not off by a tooth and retarding the timing. In my experience it's all too easy to be off by a tooth when installing a 3FE distributor. If you have in correct then that's great and I suggest you bump up the base timing to around 9-10 degrees instead of 7.
 
Godwin said:
I think you need to recheck the timing to make sure that the distributor is not off by a tooth and retarding the timing. In my experience it's all too easy to be off by a tooth when installing a 3FE distributor. If you have in correct then that's great and I suggest you bump up the base timing to around 9-10 degrees instead of 7.
Click to expand...
Thank you for the suggestion. I actually thought of this last Saturday and re-stabbed the distributor 1 tooth to the left. Not good, and barely cranked. I have set it to 7 degrees and played with the timing to try and get it to rev.

Do you think a failing ignition module could cause random misfires at all temps and failure to rev off idle?

I have pics of ignition waveforms at distributor, igniter input, and coil trigger wire, if anyone here would like to help analyze.
 
WrenchMagnate said:
Thank you for the suggestion. I actually thought of this last Saturday and re-stabbed the distributor 1 tooth to the left. Not good, and barely cranked. I have set it to 7 degrees and played with the timing to try and get it to rev.

Do you think a failing ignition module could cause random misfires at all temps and failure to rev off idle?

I have pics of ignition waveforms at distributor, igniter input, and coil trigger wire, if anyone here would like to help analyze.
Click to expand...

When you set the timing are you connecting the E1 and TE1 ports with a wire? These are in the small black box under the hood at the firewall, passenger side.
 
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