1UZ swap, idles fine, no power

[Ryno5150]

85 4Runner, 1UZ/R150f swap. FINALLY got it running last summer, and it ran like a champ. Took a trip to Moab (...that's pretty much a side view, not a pic from above) in October. Ran fine, but my mocked up power steering pressure line blew up and soaked my wiring and alternator with ATF. Parked it for a few weeks while I was in GA. Got back, got a real power steering line fabbed up. Test drive...no power above roughly 2500 RPM (no tach, guesstimate). RPMs drop to idle. Same exact thing if attempting anything throttle application of over 60 or 70%. Can hold gas pedal to floor and NOTHING happens. Stays at idle. The longer I drive it, the worse it gets - I took it out for a several mile drive - it was semi tolerable at first, eventually could barely creep up gradual inclines on the way home. Here is what I have done: disconnected exhaust before cat converter (it's new) - no change. Smoke tested - NO vacuum leaks. Swapped in a spare ECM - no change, nephew sent me a spare ECM he had - no change. Opened up one of the ECMs to check for failed capacitors or any other suspicious looking stuff - looked fine. Gave MAF to my nephew to test on his 95 1UZ swapped 4Runner - he said it ran just fine. Swapped in spare TPS - no change. Checked timing - all timing marks line up. The old fuel pump holder/sending unit was very corroded and the wires were hanging by a few strands - replaced holder and fuel pump with a slightly higher volume pump - no change. Unwrapped any wiring that got hosed down with ATF, cleaned, rewrapped. Took alternator to O'Reilly to test - passed. It charges at 13.98 - 14.02V @ about 2000 RPM. Checked wiring from TPS to MAF to ECM - all ohmed at 0.3 or less. Checked resistance on coils - withing spec. Checked resistance on cam and crank sensors - within spec. Wiring from cam and crank sensors ohmed out 0.3 or less. No blown fuses. Swapped in spare igniters today...after startup, first test drive up the driveway - it hauled ass like it is supposed to...then each subsequent test run up the driveway, it got worse and back to square 1. It runs super rich, like a carburetor out of tune. The IAC has been giving me fits from day 1. It will not work. I even bought a new one. Nothing. So I rigged up a valve and put in the IAC - to intake tube hose, essentially creating a manual choke to control air flow- but that setup gave me zero issues pre- Moab. It ran fine. One of the wires to the IAC connector is almost completely severed. It still shows continuity, but questionable whether it can handle a load. New rotors, caps, ignition wires, spark plugs. At this point, I'm out of ideas. This is Kelvin from CartuneNZ territory now. Any ideas would be greatly appreciated. Engine is from a 1991 LS400.

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[liveoak]

sounds like you're on the right track. I would assume it has something to do with the ATF soaking. picture of the engine bay? does a 91 1uz have a way to check codes with a jumper or something? it ran fine when cold and then ran bad? something to do with entering closed loop? try different O2 sensors? intake restricted?

 

[mesa man]

It sounds like” limp mode” symptoms.
Years ago our 2uz in a 100 series had issues like yours, IIRC I cleaned the intake plenum, disconnected battery to reset and it fixed the issue, happened one other time while driving, no power , just idle no matter if I floored it. That time I just disconnected and cleaned battery connections and it reset.
I would do a search of 1uz limp mode symptoms and solutions.

Good luck , cool truck!

 

[Ryno5150]

sounds like you're on the right track. I would assume it has something to do with the ATF soaking. picture of the engine bay? does a 91 1uz have a way to check codes with a jumper or something? it ran fine when cold and then ran bad? something to do with entering closed loop? try different O2 sensors? intake restricted?

I unwrapped any sections of harness that got ATF soaked, sprayed down with electrical contact cleaner and re-wrapped. I did replace my alternator yesterday, as voltages were bouncing all over the map. Here is the weird part. I swapped igniters with a spare pair, and it ripped up the driveway (it's a long enough driveway to get some good runs) like it should. 2nd try...back to stumbling and dropping out. I also adjusted the TPS full counter clockwise...same thing, it hauled ass up the driveway on the 1st run, then the subsequent runs it ran like crap. I can hold the accelerator pedal down and it just stays at idle for the most part, will pop and rev slightly. You can smell the fuel mixture getting richer and richer. It's as if the ignition timing won't advance, which is controlled by the ECM, but as I wrote in my initial post, I have tired 3 different ECMs to no avail. Seems as if the TPS signal is dropping out which in turn is affecting spark control. It does get worse the longer I drive it. I have good continuity in wires from TPS - MAF, TPS - ECM, MAF to ECM. I swapped in a spare TPS, and same thing. It seems like an ECM issue but I think it's highly unlikely all 3 ECMs are bad. I pulled the cover on one (the original that came from donor vehicle), and it looked clean

 

[Ryno5150]

It sounds like” limp mode” symptoms.
Years ago our 2uz in a 100 series had issues like yours, IIRC I cleaned the intake plenum, disconnected battery to reset and it fixed the issue, happened one other time while driving, no power , just idle no matter if I floored it. That time I just disconnected and cleaned battery connections and it reset.
I would do a search of 1uz limp mode symptoms and solutions.

Good luck , cool truck!

Thank you! It's a fun truck...when it runs properly. I have been combing all the Lexus forums for anyone who has had similar issues. If you read my reply to liveoak, I have some updates of what is going on. It's maddening that it ran so wonderfully and now it's running like poo. I need to get this wrapped up so I can go all in on my FJ40 restoration.
What mountain is that in your pic? I'm an avid hiker and state high pointer, so always interested in peoples' hikes.

 

[gnob]

i wonder if you have a temp sensor weirding out.
sounds like a temp sensative thing.
i would double check continuity and resistance values while it's in fail vs cold.

 

[mesa man]

Thank you! It's a fun truck...when it runs properly. I have been combing all the Lexus forums for anyone who has had similar issues. If you read my reply to liveoak, I have some updates of what is going on. It's maddening that it ran so wonderfully and now it's running like poo. I need to get this wrapped up so I can go all in on my FJ40 restoration.
What mountain is that in your pic? I'm an avid hiker and state high pointer, so always interested in peoples' hikes.

It sounds like that ATF got in everything!

Cool man! That’s NM highest point Wheeler peak near Toas at 13,160 Northern New Mexico Loop (NNML) a Brett Tucker route. I’ll tag you on my CDT backpacking thread if you want to follow along!

 

[Ryno5150]

It sounds like that ATF got in everything!

Cool man! That’s NM highest point Wheeler peak near Toas at 13,160 Northern New Mexico Loop (NNML) a Brett Tucker route. I’ll tag you on my CDT backpacking thread if you want to follow along!

I hiked Wheeler Peak in Sept of 2024. I knocked out Kings Peak UT, Mt Elbert CO, and Wheeler all within the space of week. It was exhausting. Tag me. I'd like to see your adventures!