I have a 1991 FJ80 3FE, and I'm having trouble figuring out what's going on with it. It starts up perfectly fine, idles around 650-800ish, and idles a little higher when the AC is turned on. When I shift into gear, reverse, or drive, visible black smoke starts coming out from the tailpipe, and the idle gets rougher; the rpms are bouncing around in the 400-500s, and the engine starts to shake. Turn the AC off, shift back into park, and the idle returns to normal and smooths out.
1991 FJ80 3FE black-smoke from exhaust when in gear and AC on? Need help.
- Thread starter ASUAREZ27
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Look for cracks/tears in the intake tube especially in the underside of the bellows section.
- Thread starter
- #3
Thank you for replying! I inspected the intake tube as you suggested, and found no visible cracks in the bellows section or anywhere else on the intake tubing. I am new to the Land Cruiser addiction, so bear with me as I am also a weekend mechanic trying to do the work myself. It has been doing this for a little while now. Initially, it threw black smoke at idle, regardless of the AC being on, and didn't run very well. I suspected the issue might be related to the air/fuel mixture, as the black smoke was present at idle. I made some adjustments to the Air mass flow clock spring after seeing others make the same adjustment on the forums, and now the black smoke is gone at idle. Still, as stated previously, with the AC on and in gear, the black smoke appears instantly, the engine idles roughly, bogs down, but doesn't shut off, and the engine shakes. I have purchased another AMF, so I can rule that out, just waiting on the part.
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- #5
Also, I forgot to mention that while all the symptoms are presenting themselves, the AC is on and in gear. If I turn the AC back off and the LC is in gear or park, it will smooth itself out, idle back to 650-800ish, and the black smoke disappears as if nothing is wrong with it.
- Thread starter
- #6
The "gear" teeth on the top portion of the picture are what I adjusted.
Black exhaust smoke is usually unburnt fuel.
Since this happens when the engine is under load, I would suggest looking for wiring issues.
With the motor under load, it will shift on the mounts possibly grounding out a set of injectors (the 3FE fires 2 sets of 3 injectors) and possibly keeping them open.
All wiring and connectors are now 34 years old and have been baking under engine heat and high ambient temps.
I would immediately stop trying to put a band aid on this issue by making adjustments to sensors that were not meant to be adjusted. The 3FE is 1st generation EFI designed in 1986 installed on a tractor motor. There's no magic to any system here, and the ECU has a very limited window to make corrections.
All mechanical adjustments MUST be correct according to the FSM first.
Idle speed should be 650 RPM at normal operating temp (AC off) without any fluctuation.
The Toyota factory service manual (FSM) and electronic wiring diagram (EWD) are invaluable for troubleshooting and can be downloaded from the resources section. You can also purchase a complete set of manuals from the link in my signature.
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