1992 FJ80 3FE hard start/won’t stay running issue (2 Viewers)

[92Basketcase]

Here’s the short version: 3FE will start and run, but shuts off after being put in gear.



The longer version is: I’ve owned this truck for 8 years. It recently failed California smog check. My local shop couldn’t get to it for several weeks, so I took it to a shop in Bakersfield, which replaced the 02 sensors and pigtails, and replaced the AFM. They reported it would now pass smog, but they could not perform the test because their computer was down and they could not estimate when it would be repaired, so I took it home.

The CEL came on during the drive home, and after resetting it, the 80 did not pass smog at the local shop.

Unfortunately, my wife’s Expedition’s trans went out, and we needed the 80 immediately for the school run. My wife drove it for a week. While I was driving kids to practice in it, it stalled and died. It would crank but not start. I noticed the vacuum line to the distributor was not connected; I reconnected it, no change. I added some gas but again no change, so I had it towed home.

At home:

• I replaced fusible link (No CEL with key in ON)
• Visually checked all fuses -all good.
• Checked EFI relay – checks good
• +12 at brass screw in relay box

Pushed open the AFM flap – engine finally started. Drove it ¼ mile, it began to stutter and died.

After this:

• I replaced fusible link again (No CEL with key in ON again)
• Replace AFM

The engine now cranks, starts, but won’t run. I wait 15 minutes – engine starts and runs normally. Moved outside of garage, stalls and dies. Will not restart.

Most recently:

• Confirm fusible links are good
• Checked continuity of all fuses with multimeter -all good.
• Checked EFI relay with multimeter – checks good.
• Check circuit opening relay with multimeter – checks good
• Check AFM terminal resistance with multimeter – checks good.

After this, the engine started and ran normally. I shifted into reverse, the engine stalled and dies. Would not restart.

I “feel” the issue is in the AFM, but the resistance at all connections seems to be right.

I jumpered Fp to B+ in the diagnostic box and the engine refused to start. Not sure what this means but I don’t see a fuel delivery issue since the engine will start and run for a short while.

Any guidance would be greatly appreciated. This truck has stranded me/refused to start numerous times for every normal reason (from dead battery, to overheated relay, to blown fuse, to bad fusible link, to opening the two screws of death) but this one has me beat.

This thread seemed promising:

91 FJ80 Engine starts then dies immediatly - https://forum.ih8mud.com/threads/91-fj80-engine-starts-then-dies-immediatly.1356002/page-2

But the resistances all measure in spec, according to this.

So, I'm out of ideas, and any help would be greatly appreciated!

 

[Devils Paw 80]

Any guidance would be greatly appreciated. This truck has stranded me/refused to start numerous times for every normal reason (from dead battery, to overheated relay, to blown fuse, to bad fusible link, to opening the two screws of death) but this one has me beat.

Damn. Have you checked the fuel pressure, or found out what the CEL code is?

 

[92Basketcase]

Its not throwing a CEL anymore (while running) so no luck there. Since it will run for several minutes in Park I can't imagine there is a fuel pressure issue?

 

[Izeloz]

Check your intake hose VERY thoroughly for cracks. I have had this problem before. It would start and run okay, but when I put it in gear, my weak old OEM motor mounts allowed the engine to move enough to open the crack(s) in the intake tube and it would die. HTH!

 

[jonheld]

^^^^^^this
And why are you blowing fusible links?
Are you testing them or are you just replacing them?
The lack of the CEL indicates that the ecu is not in a ready state. That could be from lack of power to the ecu or several other factors.
The AFM comes to mind as you mentioned removing the screws on the connector.

 

[OrangeCrusher]

regarding the AFM - just be mindful that passing the FSM resistance check does not confirm the AFM works correctly. It just means that it does something, but it does not confirm the AFM is measuring the air volume correctly.

Also given you said the AFM was replaced, and given these have not been made by Toyota or Denso for a long time, I assume it has been replaced with an aftermarket version. The experience I had with the aftermarket options you can get for the 1FZ is that they are not made that well and have at least 3 types of issues:
1. the whole flap mechanism can get stuck randomly. can be fixed by taking it it apart, cleaning it, oiling it, polishing any rubbing spots.
2. they may or may not be calibrated correctly (may lead to too lean or too rich running)
3. they do not have a linear response curve:
a) the ones I had all went super rich with wide open throttle / high rpm. Like 2x required fuel and engine stutters / dies rich.
b) the response curve itself has bumps in it. So at some throttle settings it's a bit leaner than needed, other times a bit richer. This is because the layout of the resistive mechanism itself seems simplified vs OE/Denso version leading to some aberrations

Not saying this is causing your issues, but just to be mindful of.

 

[Devils Paw 80]

Its not throwing a CEL anymore (while running) so no luck there. Since it will run for several minutes in Park I can't imagine there is a fuel pressure issue?

Right. I overlooked some of your post.
Do you have CEL with key on now? If not I'm surprised it starts at all. See above-jonheld post-and give us an update.

 

[92Basketcase]

The CEL illuminates with the key in "ON" now. (The fusible link that blew twice was the one associated with the brake light. No brake light=blown fusible link = no CEL with key in ON)
Sounds like tonight I will be checking the intake hoses and all associated vacuum lines. Since I now have two suspect AFMs, I will try disassembling and accurizing one of them. I'll update in the AM. Thanks everybody!

 

[92Basketcase]

OK, I checked the intake hoses and replaced one (since I had it in stock) and I replaced any suspect vacuum hoses. It started and idled, and ran in Reverse, but as soon as I put it in Drive it died. The fusible link blew again on restart. I'm going to try ordering (another) AFM and after that I'm out of ideas again.

 

[OrangeCrusher]

well, if the fusible link blew - that is a sign there must be something wrong with the electrical system? Likely a short somewhere?

As much as I distrust the aftermarket AFMs, I don't see how they would blow the fusible link even if wildly defective.

 

[Izeloz]

I agree. Something is causing that fusible link to blow, and it's VERY unlikely to be a bad AFM or other sensor. Figure out which one it is and get ahold of the EWD for your truck. You've probably got a damaged wire or connector somewhere, and an EWD will help you narrow down the problem.

 

[jonheld]

The fusible link(s) are a set of 3, each feeding a different subsystem.
You need to determine which of the 3 is popping and start looking downstream into that subsystem.