FJ80 3FE Intermittent Hot Power Cut (1 Viewer)

[mtnbiker4evr13]

Guess its my turn to play "Find the intermittent 3FE fault"..

Symptoms:
On trail rides on warm days idling/going slow in low range, when driving any throttle input over 1/8 to 1/4 pedal will cause the engine to cut out/stumble. Happens under load and in neutral, no codes when checked with CEL flashes.

If you shut it off and restart the problem goes away for a while. Does not happen when driven at road speeds. Seemed to occur getting back on the road after a trail in high range or running down trail at higher speeds in low range.

Zoltar's Prediction:
Searching Mud has me leaning AFM or TPS if the heat is making the ECU see major fault and going into limp mode. TPS and AFM were previously checked and TPS adjusted to spec as part of the resurrection work after I got the vehicle in February as a non runner. Have since put 2,000mi on and it runs great daily. Underhood temps are high when issue occurs.

I've also had the ubiquitous overheated EFI relay but that presents differently where it dies and won't idle, look for CEL light and it is easy to identify. After typing out when it happens I suppose the relay could be suspect if the system pulls more load at higher throttle inputs.

Previous work:
New plugs(ngk), wires(intermotor), cap/rotor(oem), intake boots(oem), coolant temp switch/sender(oem), EFI Relay(oem), fully desmogged..

Pictures for interest:

So, wanted to cast the question out to the wider cumulative awesomeness of Mud before I just parts cannon since its hard to get it into the failure mode predictably. It runs amazing the other 99.9% of the time albeit somewhat turdish with 37s/stock gears and gets 11mpg. I like the 3FE so a swap is not in the plan

 

[jonheld]

AFM or TPS if the heat is making the ECU see major fault and going into limp mode.

If that were the case, you'd get an error code.

The most common issues would be an intermittent fusible link or poor/corroded crimps/loose terminals in the relay box.
I would suggest a bit of "percussive diagnostics". Give the EFI relay a tap tap tap as well as connector EB1, which runs the show for all of the +12 for the EFI system.
Current draw across the EFI relay remains pretty constant throughout the RPM range.

 

[mtnbiker4evr13]

If that were the case, you'd get an error code.

Would that code be hard stored to be retrieved after the key is turned off?

Also hoped you would chime in. I appreciate it!

 

[jonheld]

Would that code be hard stored to be retrieved after the key is turned off?

Yes. Codes are stored in memory. Active codes will throw a CEL when the engine is running and the CEL can clear on its own, but the code remains in memory.
This is why it's important to clear codes when troubleshooting. This way you know you're not looking at an old code.

 

[mtnbiker4evr13]

Makes sense, didn't know if this ODB1 had volatile codes or if it was just there vs not there. Will do more digging on power side since EFI relay was already suspect.

 

[ppc]

@mtnbiker4evr13 ,
The conditions you've described are all under high load where the engine is going to be rotate/movement so I would look at damaged wiring harnesses or connectors.