Intermittent power loss 91 landcruiser

[LS1FJ40]

You don't replace the black box. The fusible links are the two links going to the black box and the one going to the grey connector. They come together as a set. They are about $14 from your dealer.


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[Flylow 72]

Thx.

 

[jonheld]

Cleared codes, now cannot recreate problem. Ready to pull my hair out. With regard to fusible links I'm guessing I should just replace the black junction box and the small grey connector.

Don't pull your hair out. You're chasing down an intermittent problem which is the most difficult to troubleshoot. We will all hold your hand and wipe away your tears while you go through this and you will be better off in the end.

 

[jonheld]

Again, excuse my ignorance. Could you clarify "jump pins 3 through 6".

My fault. I should have clarified.

 

[jonheld]

Cleared codes, now cannot recreate problem. Ready to pull my hair out. With regard to fusible links I'm guessing I should just replace the black junction box and the small grey connector.

After clearing the codes when you first started the engine was the idle slightly higher than normal? Was it different at all?

 

[LS1FJ40]

Cleared codes, now cannot recreate problem. Ready to pull my hair out. With regard to fusible links I'm guessing I should just replace the black junction box and the small grey connector.

We've all been here at one point. And thankfully you have @jonheld helping you. There is nobody more knowledgeable when it comes to the 3FE. Period. Follow his guidance and he will help you get this resolved.

Don't jump around. Listen to him. Follow his directions. He is telling you to do certain things and asking you specific questions for a reason.

I'm guessing he's asking you about the high idle because you should get a high idle after the ECU is disconnected from power. Maybe Jon can elaborate why this is important to know.


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[jonheld]

@Parsnip is right on the money as well.
We're all here to help.

When you remove power from the ECU it clears out any stored codes that may or may not have thrown a CEL, and it also forces the ECU to relearn all of the sensors. It takes a bit of time for the capacitors to discharge until the ECU "forgets" and "reboots".
I have always noted a change in idle speed on the first start when this happens. She will tend to stay high for the first few drive cycles, then settles back down to 650 after the ECU knocks the ISC valve back.

 

[LS1FJ40]

@Parsnip is right on the money as well.
We're all here to help.

When you remove power from the ECU it clears out any stored codes that may or may not have thrown a CEL, and it also forces the ECU to relearn all of the sensors. It takes a bit of time for the capacitors to discharge until the ECU "forgets" and "reboots".
I have always noted a change in idle speed on the first start when this happens. She will tend to stay high for the first few drive cycles, then settles back down to 650 after the ECU knocks the ISC valve back.

I've heard people say it takes 3-4 15+ minute drive cycles to get the idle to come back down to 650. I've often questioned this because sometimes it only takes one. Other times it takes four. I don't think there is a set number. Is this correct?

Seeing as the OP doesn't know the history or age (possibly 24 years old) of his fusible links (and their relative low cost) do you think it's advisable to go ahead and replace it anyway? Or get the fusible link but don't replace it yet to see if the intermittent problem comes back then replace the fusible link?


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[jonheld]

I've heard people say it takes 3-4 15+ minute drive cycles to get the idle to come back down to 650. I've often questioned this because sometimes it only takes one. Other times it takes four. I don't think there is a set number. Is this correct?

Seeing as the OP doesn't know the history or age (possibly 24 years old) of his fusible links (and their relative low cost) do you think it's advisable to go ahead and replace it anyway? Or get the fusible link but don't replace it yet to see if the intermittent problem comes back then replace the fusible link?


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I think the amount of time it takes to relearn is dependent on several factors. The type of driving, the length of driving, and the ambient conditions.
It is similar for the 1FZ-FE. Whenever I'm under the hood for a tune up or anything where parts are getting removed, I pull the EFI fuse and let the system relearn.
The 3FE is 1986 technology and first generation EFI. The 1FZ-FE is somewhat more advanced and more controlled, but still 20+ year old tech.

The fusible links are very inexpensive and can be purchased online and shipped to your door for a reasonable price. I like to check things with a meter, but at 25 years old they don't really owe you anything. Since power is everything, it would be good practice to simply replace them.

 

[LS1FJ40]

Yeah, I like the old technology! It's simple!

And that's what I thought on the fusible links. I finally got my bastardized fusible link fixed. The stereo installer had cut the wiring harness 10-12 years ago and put in an 80amp inline fuse. Found a totaled 80 and cut the grey plug and spliced it in so I have a full three fusible links now!

When I replaced the old fusible link (well, the two remaining that go to the black box) they were very brittle and crumbled when I pulled them out. It only makes sense to replace it.




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[Flylow 72]

When I started the engine, it did seem to idle a bit higher around 825rpm. After a short drive, maybe 10 min run time, idle at 650. Ordered fusible link from Toyota.

 

[Flylow 72]

Replaced fusible link today. Upon closer inspection after I removed the old one, I found crack in the insulation which exposed wire to the black junction box. Not sure this is the smoking gun, but considering how cheap the part and the ease of replacing it, couldn't hurt. The truck seems to be running fine now and I still can't get the problem to reoccur. Would it be worth "jumping the pins"and trying to read the CEL codes even though problem has not happened since I reset the ECU by pulling fuse?

 

[LS1FJ40]

Well, bare wires is never a good thing. Certainly if the wires were getting moved and josseled around then they could be the issue.

I'd certainly say this is "solved?" As in, probably but don't know for sure.

At Jon said though, the fusible links were 24 years old. They didn't owe you anything.

 

[savvy]

91 Landcruiser, 167k. Sat for 8 months, started right up drove for 700 miles no problems. Now after warm up or roughly 2 mile drive, rpm will drop to idle when it reaches 1400-1600. Will actually stall and engine will quit when driving sometimes. When vehicle is parked rpm will just drop from 1400-1600 to idle and engine won't stall. No CEL.

What has been done: I'm including everything since we fired it up in Nov., to leave no stone unturned.

Added fuel injector cleaner

Replaced: starter
inline fuel filter (found h20 on pump side of line)
fuel pump
distributor cap, rotor and harness

I have read quite a few posts on here with regard to these types of issues, and I believe some lucky 80 owner has experienced this same problem, unfortunately posts often end with no resolution. At any rate vehicle is located on the North Shore of Kauai, anyone who has been here would know resources are limited.
Any ideas will be greatly appreciated.

Having had the exact same symptoms after having replaced my dizzy cap, rotor, air filter and plugs..............
Culprit was the Air Flow Meter hose.
Improvement when wrapped with cellophane.
It was cracked.....probably when I either bent it back for the air filter or pushing against it to get access to dizzy/plugs.
After replacement.....runs and idles fine.
My bet is there.
Cheers!!!

 

[jonheld]

Replaced fusible link today. Upon closer inspection after I removed the old one, I found crack in the insulation which exposed wire to the black junction box. Not sure this is the smoking gun, but considering how cheap the part and the ease of replacing it, couldn't hurt. The truck seems to be running fine now and I still can't get the problem to reoccur. Would it be worth "jumping the pins"and trying to read the CEL codes even though problem has not happened since I reset the ECU by pulling fuse?

When you disconnect power from the ECU for 10 or so minutes, either by pulling the EFI fuse or removing the battery terminals, all stored codes are cleared from memory. Until the problem reoccurs, or another sensor goes outside of its specification, there should be nothing to read.

Drive the hell out of it.

 

[Flylow 72]

Having had the exact same symptoms after having replaced my dizzy cap, rotor, air filter and plugs..............
Culprit was the Air Flow Meter hose.
Improvement when wrapped with cellophane.
It was cracked.....probably when I either bent it back for the air filter or pushing against it to get access to dizzy/plugs.
After replacement.....runs and idles fine.
My bet is there.
Cheers!!!

Any chance you could post a picture of the Air Flow Meter Hose. Thx

 

[jonheld]

Any chance you could post a picture of the Air Flow Meter Hose. Thx

Again, this was one of the things mentioned when we spoke. He's referring to the large black tube between the air cleaner and throttle body. They become brittle over time and develop cracks on the underside. This mostly manifests itself as rough idle that smooths out when throttle is applied, or in severe cases it will cause the engine to stall in reverse at lower RPM.

 

[Flylow 72]

I already inspected that part as per your advice just didn't know it was called an airflow meter hose. My bad.

 

[jonheld]

I already inspected that part as per your advice just didn't know it was called an airflow meter hose. My bad.

No bad. Only good things.

 

[Flylow 72]

All right, back again. Problem has resurfaced. Jumped pins 3 and 6, steady blinking CEL which should mean no codes thrown. Truck has been running well for about 600 miles or so, driving yesterday, lost power at about 1500 rpm, stalled, restarted and idled fine. Tried it a couple more times same thing. Let it sit about 15 minutes fired it up and drove it home without a hiccup. What's next?