1991 3FE running rough/instant change (1 Viewer)

[STICKP]

Hi Everyone,

I'm new to this forum so forgive me if I have posted something already covered. I could not find exactly the same scenarios as my troubles.

I was driving down the highway at 65mph, when instantly I lost power. From that point forward, it sputtered and ran horribly. I could hear what sounded like an exhaust leak.

Sure enough, the downpipe had rusted through in a spot. I fabricated a cuff for it to get me through the trip although it still ran bad, but better than without the cuff.

On my return, I took it to a muffler shop and got new down pipes and cats installed....still ran horrible.

It had code 51 and 02 codes. I changed the TPS and the 02 sensors. CEL disappeared, but TPS code still present.

I've chased everything since -

Plug wires, plugs, distributor cap, fuel filter, fuel sock, new intake hoses (old ones were horribly cracked), cleaned throttle body but did not remove it...

I checked the timing this weekend, Ohms on the TPS, Ohms on the AFM.

At first the AFM was off. I opened the top, found a metal tab to be loose, soldered it, and then got the correct ohms...

Still, it's running terrible. At 55mph, the thing sound like a helicopter inside.

I'm at a loss. Any help would be greatly appreciated.

 

[STICKP]

Also, I should mention. With each new part, etc, the truck seemed to run a little better. It's markedly better now that directly after the exhaust work, but nowhere near smooth.

 

[sea bass]

Maybe somthing internal timing gear broke ,bent pushrod or valve

 

[91 AV Pig]

None of the following will explain your sudden loss of power and poor running afterwards, but are things that can cause issues.

-Check the timing
-Replace the O2 sensors
-Replace all small vacuum lines, which are all 26+ years old
-Clean-out or replace all EGR components - they get crusted with carbon deposits
-Replace the PCV valve and grommet
-The 3FE is sensitive to valve adjustments and the Toyota manual calls for adjustments every 15k miles. Poorly adjusted valves will sound like tapping or rattles if tight or loose. Replace valve cover gasket and rubber washers under bolts
-The fuel pressure regulator (FPR) and the fuel dampener can easily be replaced

Finally, ask Jon Held (@jonheld), he is one of the 3FE gurus on the board

Good luck

 

[STICKP]

Thanks for the responses @sea bass and @91 AV Pig - I haven't messed with the EGR components and I haven't adjusted the valves in the 25,000 miles I've owned it. It's sitting at 154k right now, so I'm sure that's in order. Thanks!

Any ideas about the sudden loss of power or any other symptoms described @jonheld ? And thanks much in advance.

 

[sea bass]

It's hard to say without seeing it in person maybe an air flow meter

 

[jonheld]

Hi Everyone,

I'm new to this forum so forgive me if I have posted something already covered. I could not find exactly the same scenarios as my troubles.

I was driving down the highway at 65mph, when instantly I lost power. From that point forward, it sputtered and ran horribly. I could hear what sounded like an exhaust leak.

Sure enough, the downpipe had rusted through in a spot. I fabricated a cuff for it to get me through the trip although it still ran bad, but better than without the cuff.

On my return, I took it to a muffler shop and got new down pipes and cats installed....still ran horrible.

It had code 51 and 02 codes. I changed the TPS and the 02 sensors. CEL disappeared, but TPS code still present.

I've chased everything since -

Plug wires, plugs, distributor cap, fuel filter, fuel sock, new intake hoses (old ones were horribly cracked), cleaned throttle body but did not remove it...

I checked the timing this weekend, Ohms on the TPS, Ohms on the AFM.

At first the AFM was off. I opened the top, found a metal tab to be loose, soldered it, and then got the correct ohms...

Still, it's running terrible. At 55mph, the thing sound like a helicopter inside.

I'm at a loss. Any help would be greatly appreciated.

Lets back up a bit.
Were any codes present before the loss of power or were they coincident with the loss of power?
Was ANYTHING done to the truck prior to the loss of power?

Screwing with the AFM is not something I would recommend. If it questionable, pick up a good used one from any 3FE equipped Land Cruiser (88-92).

A loss of backpressure would cause power loss. Depending on where the hole was, hot exhaust could have burnt through wiring or anything else close by. Inspect everything in the area.

Another possibility is something let go in the ignition system causing a backfire which blew a hole in the weakest link. Check plugs for missing electrodes, check wires for cracks or simply replace if they're past due.

I doubt that it would be something sinister internally.

 

[STICKP]

Thanks for the reply @jonheld

Yes, prior to the loss of power, there was a code for TPS and 02 sensor. Neither were coincident with loss of power.
Nothing was done to the truck prior to loss of power.

I assumed the loss of back pressure was the problem as the hole was just before the outside cat.

I changed the plugs, wires, rotor, and dist. cap and saw nothing to indicate a problem....replaced anyway.

I'm glad to hear that it may not be something internal.

I'll keep trying to chase it and report back when I find the culprit. Thanks again!

 

[sea bass]

Can you explain what you mean when you said it sounds like a helicopter inside

 

[STICKP]

@sea bass When I get the truck up to 55 which takes quite a while with the pedal completely depressed, as soon as it shifts and the RPM's lower, it shakes, like a manual would if you skipped a gear. It honestly is exactly the same as what happened when my exhaust sucked the rust through initially. Seems like something's off with the air/fuel ratio.

 

[FranceJohnson]

My truck was running very similar to that when the timing was jacked up. I would probably put double checking that and your dizzy on the list.

 

[FranceJohnson]

I remembered another thing that happened to me last summer. My truck would run fine for the first trip of the day, but if I turned it off and drove again it would run like that. The first thing that popped up in a search was the fuel pressure regulator and fuel damper. I changed mine with no luck. It ended up being my temperature switch wiring harness plug was busted. My engine was doing wonkey stuff with the timing and ratio from bad data. You're on the right track, it takes some time to figure out what is happening.

 

[jonheld]

My truck was running very similar to that when the timing was jacked up. I would probably put double checking that and your dizzy on the list.

Ignition timing is not something that will change suddenly unless the distributor housing is loose and flopping around.
It is possible, however unlikely, that the distributor driven gear pin broke and is allowing timing to change, but the engine probably wouldn't run at all in that case.

 

[sea bass]

You mentioned you changed the plugs and wires are you sure you have the firing order right, i think i would start at your afm

 

[STICKP]

Thanks @FranceJohnson. This is reassuring, and thanks to all who have chimed in. I've got a plan for this weekend. Will report back with progress and hopefully will find a solution.

 

[Michael Hanson]

Hi, How are the rpms and speed ? Are the rpms increasing but the speed not increasing ? Long time to get to 55mph . Noise ,rattle? Torque converter? I'd also pull the spark plugs and check the vacuum to see how the valves are . Mike

 

[ml111]

Hope this helps: I was driving my 1992 FJ80 on the highway one time and it suddenly started sputtering, shaking and running horribly. It turns out that the PO had done some work on the fuel injectors and forgot to appropriately insulate and isolate the wires, eventually, the heat from the air injectors melted the insulation in the fuel injector wires causing a short and 3 fuel injectors went crazy. Replaced wiring and injector connectors (NIP-T-F2 Denso Style Top Slot Female, Connectors Fast, LLC) and it solved the problem (Thank you Jon Held for helping me figure this one out).

 

[STICKP]

Sorry for the delayed update. Sickness seems to be the norm in our household lately.

At any rate, I replaced the cold start timing sensor as I was getting no read on that.

My temperature sending unit wire looked fried. I replaced the sending unit and a new connector.

While I was at it, I replaced the coolant temperature switch as well.

The 3FE is running good now, finally!!! Thanks for all the advice and help.

Now, it's time to rebuild the knuckles. The fun never stops!

 

[STICKP]

UPDATE - Cruiser ran good for a while and then kept getting progressively worse. I did narrow my symptoms down to the ISC valve (started another thread HERE to address that problem. In trying to diagnose that problem, I found that my wiring harness was burned through where it was laying on the air manifold port. Please refer to the link above to continue following this conversation.

 

[Daniel Hurst]

Mine ran rough on the highway and then it ran fine, an hour goes by and it ran very rough, could not get it to go past 10 mph, got home and next day it was totally fine, no issues, culprit was a fuel filter