Hesitation / Bucking / Stumbling 1989 FJ62 3FE (1 Viewer)

[jesus888]

Let’s get a separate thread going from my Hesitation / Bucking / Stumbling issue that I reference in my build thread because I’d like to consolidate the info in one place and hopefully get some guidance…

First I’m gonna link a few very short videos that show what the truck is doing… it happens under load, and also in a parking spot, it happens when it’s cold, it happens when it’s hot, I’ve got parts ready to go on that continues my “throw parts at it” approach but I’m running out of ammo.

3 Videos

• FJ62 3FE hesitation Part 3 - https://youtu.be/oYftMRwTDkw

Here’s the history I know and I may be forgetting some things…

• Truck had a cracked head a few years ago due to overheating
• PO had the engine rebuilt by a shade tree mechanic, but with references, and all OEM new parts. I’ve had multiple mechanics agree that they see nothing that appears to be corners cut in the rebuild, engine has healthy compression
• Engine has had the current issue since rebuilding, but not before.
• I had it shipped (when I purchased it) directly to a local Japanese car mechanic (excellent guy with lots of knowledge - details in my build thread) and he couldn’t figure it out in the time that he had it, although we ruled out quite a few things… including the EGR (because we desmogged), Fuel system (we replaced most of it and verified pressure)
• I brought it home in time to get to appointment time with @cruisermatt in early Aug for my H55f swap and he did a few things to try and rule out some issues, but it was time for the FJ62 to come home and we didn’t get a chance to fully put the issue to bed…
• And that brings us to present… I didn’t experience the issue for a couple of days, and now it’s happening all of the time.
• When it’s not having the intermittent issue, it runs STRONG and comfortable to drive… when it is having the issue (for 30 seconds or for 5 min at a time) it’s MISERABLE and not Driveable (lots of hazard lights )

Items replaced / tested / ruled out

• Fuel system shows good pressure (verified by @cruisermatt ): New Fuel Pressure Regulator, New Fuel Pulsation Dampener, New OEM Fuel pump, New Fuel injector pigtails
• Vacuum system shows good vacuum (verified by @cruisermatt ): New Intake hoses, and pulling vacuum to make sure that was unlikely an issue
• AFM has been checked based on FSM and passed all tests. It is not OEM FJ62, not sure what it’s from, but it was also on the rig prior to the engine rebuild (my understanding) and there wasn’t an issue with it. I do have a 1993 Toyota Camry AFM that I am going to be cleaning up and popping in to see if that helps (got it from a local Pull-a-part)
• I still have all of my tune-up parts on the shelf (plugs, wires, cap and rotor, etc) and will get to that but only WHILE I’m troubleshooting this issue…
• I see new-ish sensors on the Thermostat housing, and I will assume they were replaced during the engine rebuild but I have not run any tests on them.
• All major grounds and power cables have been replaced with @Fourrunner ’s kit along with @ToyotaMatt ’s fusible link. I was really hoping this was going to solve the issue… but alas, it has not.

 

[jesus888]

Also to note alternator connections have been cleaned and 13.99 volts coming from alternator at idle and battery shows 13.84 volts using multiple grounding spots…

 

[Fourrunner]

Major vacuum leak like the intake manifold bolts are loose? You mentioned head work.

 

[jesus888]

Also EFI Relay was replaced and fuel pump relay under passenger side dash has been replaced.

 

[jesus888]

Major vacuum leak like the intake manifold bolts are loose? You mentioned head work.

Vacuum is strong and consistent… last person to verify that and the fuel pressure being great was @cruisermatt last week before it left his place. He also experienced some of the hesitation / stumbling. He mentioned that during one of his drives, when it started doing it, he pulled off into a field and bounced around a bit and it stopped doing the hesitation… that along with the video of me revving in neutral are more anecdotal and not necessarily repeatable, but just notes to help frame the issue…

 

[OSS]

Since you’ve replaced virtually everything related to fuel delivery which your symptoms all pointed to (bucking, hesitation, stumbling), and a petering out ignition system typically doesn’t present those symptoms, my mind is venturing towards the dark side: ECU malfunction.
I have no experience with the the 62 to back up this guess but the quivering scaredy-cat in me is going to places I dare not ever tread — dying ECU.

 

[ToyotaMatt]

Vacuum is strong and consistent…

well ,,,,,,

- How Strong is strong is your strong vacuum ?

- define " Consistent "

- in fact i would like a Short TECH Video showing each of the issue Please ...


thanks matt

 

[jesus888]

well ,,,,,,

- How Strong is strong is your strong vacuum ?

- define " Consistent "

- in fact i would like a Short TECH Video showing each of the issue Please ...


thanks matt

I’m gonna let @cruisermatt answer that one but I’ll also in the meantime get ahold of a vacuum gauge and maybe a fuel pressure gauge since I’m probably going to need them in the near future!

 

[cruisermatt]

My vacuum gauge showed a very smooth 19-20 in-hg at idle. I don't belive there is a mechanical problem with the engine itself at all. When the truck is running correctly it runs very strong and smoothly and is really one of the best 3FE/H55 FJ62's I have driven actually.

More background - we replaced all electrical connector housings (pretty much all wee cracked and brittle) in the engine bay besides the o2 sensor connectors which were in good shape. At this time we verified every wire on the engine harness had correct voltage/ground per the FSM and that was fine.

What I am realizing now is that we have NOT verified fuel pressure is while the issue is actually occurring.
I think next step would be to install a fuel pressure gauge in the cabin so it can be seen in real time when the issue occurs.

 

[jesus888]

My vacuum gauge showed a very smooth 19-20 in-hg at idle. I don't belive there is a mechanical problem with the engine itself at all. When the truck is running correctly it runs very strong and smoothly and is really one of the best 3FE/H55 FJ62's I have driven actually.

More background - we replaced all electrical connector housings (pretty much all wee cracked and brittle) in the engine bay besides the o2 sensor connectors which were in good shape. At this time we verified every wire on the engine harness had correct voltage/ground per the FSM and that was fine.

What I am realizing now is that we have NOT verified fuel pressure is while the issue is actually occurring.
I think next step would be to install a fuel pressure gauge in the cabin so it can be seen in real time when the issue occurs.

I believe that before when it was with my mechanic locally, when the issue would happen the fuel pressure would be up and down with the stutter… but I’ll definitely get the external gauge to verify that.

 

[c2dfj45]

Have the injectors been tested/replaced or cleaned? Gaskets/seals for them are available from Toyota...good time to replace if you’re pulling the injectors.

 

[jesus888]

Have the injectors been tested/replaced or cleaned? Gaskets/seals for them are available from Toyota...good time to replace if you’re pulling the injectors.

You know… the engine was rebuilt 5K miles ago, so I would think that stuff has been done but we are definitely going to be doing it ourselves as we peel back the onion.

 

[jesus888]

List of items to do (in order they’ll be done)

1. Clean a replace the AFM with the Camry AFM I have
2. Hook up a vacuum gauge and fuel pressure gauge that I can see inside the 62 so I can see what impact the stumble has on those 2 things when it stumbles
3. Test and clean the cold start injector while we’re hooking up the fuel pressure gauge
4. Test and possibly Replace the EFI relay that we installed in lieu of the NLA EFI relay
5. Continue with my tune-up stuff… cap, rotor, plugs, wires, etc…
6. Maybe adjust the valves because they’re loud…

 

[cruisermatt]

getting fuel pressure gauge readings in the cab while it's driving is #1.

 

[jesus888]

getting fuel pressure gauge readings in the cab while it's driving is #1.

I had the AFM sitting here already so I went ahead and did that this AM

 

[Bob62]

The "stealer" suggested I replace the AFM. I did, but it turned out to be the TPS. Throttle Position Sensor. Fixed everything.

 

[jesus888]

The "stealer" suggested I replace the AFM. I did, but it turned out to be the TPS. Throttle Position Sensor. Fixed everything.

It’s on my list to evaluate my TPS… but it’s been about 200 miles and at least 15 separate start/drive situations since I’ve had my stumble (since replacing AFM)

 

[fruitjack]

longshots - check the o2 sensors and the state of the muffler; i had weird issues with rpms and the like due to a clogged muffler. bad o2 sensors also led to intermittent stumbling. and check out the ecu if you haven't yet. years ago i pulled mine out and discovered slight water damage to it (and an obvious PO hack

 

[FJ Silver]

In the 2 video's the valve lash ticking / injectors. Is that the normal amount of noise ya'lls 62's make?

My mind goes to TPS. Although it seems almost too bad at high RPM for a TPS malfunction.
Or fuel delivery, but you ruled that out.
I'd try another ECU to @OSS his point.. I bought one for pretty cheap to have as a backup. At 285k miles, anything can need replacement.

 

[89BIGBLUE]

Check/test temp sensor on thermostat housing per FSM.
I had one go bad on me, similar behavior.
New unit fixed it right up.
Beware, there are different part numbers for this part between the FJ62 3FE, and the early 80 series 3FE, if I recall correctly.