1991 LC80 3FE stalls at high speed (3 Viewers)

[drpotatoez]

Hello

Has anyone had an issue with their 80 series throwing the CEL, misfiring and ultimately stalling only when going above 40 mph?

My lc80 starts fine, no rough idle or anything. Drivers perfectly until I go above 40 mph. Then it will start misfiring, the tachometer goes crazy and stalls. When I try to restart it if I don’t hold the accelerator to the max it won’t start, and then I can’t put it into reverse because it immediately stalls.

If it let it sit for like 10 minutes, it starts back up fine and I can in reverse without issue.

I have cleaned the distributor cap and rotor, replaced spark plugs and wires. Before, it wouldn’t rev higher than 2000rpm and only after I cleaned the VAF, it started accelerating properly. But now this issue is present

 

[drpotatoez]

Hello

Has anyone had an issue with their 80 series throwing the CEL, misfiring and ultimately stalling only when going above 40 mph?

My lc80 starts fine, no rough idle or anything. Drivers perfectly until I go above 40 mph. Then it will start misfiring, the tachometer goes crazy and stalls. When I try to restart it if I don’t hold the accelerator to the max it won’t start, and then I can’t put it into reverse because it immediately stalls.

If it let it sit for like 10 minutes, it starts back up fine and I can in reverse without issue.

I have cleaned the distributor cap and rotor, replaced spark plugs and wires. Before, it wouldn’t rev higher than 2000rpm and only after I cleaned the VAF, it started accelerating properly. But now this issue is present

Stalling / misfiring while driving

Video of it having trouble starting

 

[CJF]

Did you pull the codes?

 

[drpotatoez]

Did you pull the codes?

No, i bought this car 2 months ago and there are so many things disconnected but the CEL never stays on. Only flashes when it is failing/stalling/ misfiring

 

[jonheld]

No, i bought this car 2 months ago and there are so many things disconnected but the CEL never stays on. Only flashes when it is failing/stalling/ misfiring

That's because the engine is stalling. That's not throwing a code. A code would be a constant CEL while the engine is running.
I would be checking the large rubber plenum downstream of the AFM (air flow meter as Toyota calls it). Any tear in that plenum will cause unmetered air to enter the system causing all sorts of problems.
BTW, how did you clean the AFM??
You didn't remove the 2 Phillips screws on the connector housing, did you??

 

[drpotatoez]

That's because the engine is stalling. That's not throwing a code. A code would be a constant CEL while the engine is running.
I would be checking the large rubber plenum downstream of the AFM (air flow meter as Toyota calls it). Any tear in that plenum will cause unmetered air to enter the system causing all sorts of problems.
BTW, how did you clean the AFM??
You didn't remove the 2 Phillips screws on the connector housing, did you??

No, the connector housing was not removed. I removed the whole unit and used a contact cleaner to remove all the crust and dirt. After this cleaning the truck started running way way better, it removed the issue where it wasn’t going past 2,000 rpm while in gear.

 

[drpotatoez]

That's because the engine is stalling. That's not throwing a code. A code would be a constant CEL while the engine is running.
I would be checking the large rubber plenum downstream of the AFM (air flow meter as Toyota calls it). Any tear in that plenum will cause unmetered air to enter the system causing all sorts of problems.
BTW, how did you clean the AFM??
You didn't remove the 2 Phillips screws on the connector housing, did you??

The plenum is still in tact, no cracks or weird bends.

 

[jonheld]

The plenum is still in tact, no cracks or weird bends.

Did you check the underside of the bellows?

 

[drpotatoez]

Did you check the underside of the bellows?

View attachment 3554102

View attachment 3554103

Yes, no cracks

 

[jonheld]

the tachometer goes crazy

What does this mean?

 

[drpotatoez]

What does this mean?

The revolutions start jumping up and down, very unstable. I posted a video of what it is doing, this thing is really eating at me

 

[jonheld]

The revolutions start jumping up and down, very unstable. I posted a video of what it is doing, this thing is really eating at me

The tach signal comes from the igniter. Are engine RPMs somewhat stable when the tach is acting up, or does the tack accurately represent what the engine is doing?

 

[drpotatoez]

The tach signal comes from the igniter. Are engine RPMs somewhat stable when the tach is acting up, or does the tack accurately represent what the engine is doing?

It accurately represent what the engine is doing. When it starts doing that, the CEL starts flashing in unison. The ride starts getting really jerky and I could hear loud clanking notices up front when it does that, until it stalls completely

 

[jonheld]

It accurately represent what the engine is doing. When it starts doing that, the CEL starts flashing in unison. The ride starts getting really jerky and I could hear loud clanking notices up front when it does that, until it stalls completely

Be sure the flap in the AFM moves very easily with no binding throughout its range.
As a diagnostic, try jumping pins 1-8 on the diagnostic connector on the firewall. This bypasses all fuel pump logic (AFM/Circuit Opening Relay) and allows the fuel pump to run with the key in the ON position. Only use this as a diagnostic. Do not leave it in there.

 

[CJF]

The tach signal comes from the igniter. Are engine RPMs somewhat stable when the tach is acting up, or does the tack accurately represent what the engine is doing?

You should watch the vid; pretty crazy.

And OP, I assume you've somehow checked that you have oil pressure?

 

[jonheld]

You should watch the vid; pretty crazy.

And OP, I assume you've somehow checked that you have oil pressure?

I don't see a link to a video in this thread.

 

[drpotatoez]

Stalling / misfiring while driving

Video of it having trouble starting

@jonheld

Took it to a mechanic, he’s checking out the VAF. Will post updates soon, holding my fingers

 

[drpotatoez]

You should watch the vid; pretty crazy.

And OP, I assume you've somehow checked that you have oil pressure?

Yeah, oil pressure gauge is wonky. It wasn’t working when I bought it

 

[drpotatoez]

I don't see a link to a video in this thread.

UPDATE:

So the plug that goes into the distributor had the wires stripped and looks like it was shorting out. That was fixed and it resolved the stalling issue
.

The truck then began to accelerate sluggishly under 2000rpm with a sudden power surge, or turbo like feeling after 2000rpm. The intake was cleaned and the injectors were cleaned. It had 2 bad injectors.

 

[jonheld]

The truck then began to accelerate sluggishly under 2000rpm with a sudden power surge, or turbo like feeling after 2000rpm.

Read the entire document and pay attention to item #10 on the list.

General Tech - 3FE Tune Up Info

3FE Tune Up Info

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