So this has been an ongoing pursuit for answers with no real result. I bought a 1990 Lexus ls400 and it is my first, I am very experienced with working on cars but I’m almost to a dead end. My car has low power and sounds like a misfire. I read the codes and got upstream 02 sensors. Before this point I replaced the plugs, caps, rotors, plug wires, fuel filter, and I swapped in a different ecu with all the same thing going on. Compression is anywhere from 180-190 acrossed the board. May I mention it is my drift car now. My cats have also been gutted by the previous owner. My timing belt has lots of stretch cracks in it and I was wondering if maybe I skipped a tooth that maybe that’s my issue. But I assumed if it skipped a tooth that it would throw a misfire code. It starts without hesitation. There is more I have to say but maybe I can get a conversation going with somebody knowledgeable on here. Cheers!

 

02 sensor issues will certainly make your car run poorly, very bad. The bends on the lengthened pipes there look a bit restricting for exhaust flow, maybe, maybe not causing problems. Gutted cats are generally considered illegal everywhere you go and that's maybe not doing you any favors either, they do serve a function. But in any event..looks like an 02 sensor problem to me, if its coding for an upstream 02 sensor problem it's going to run very poorly with little power. You can try cleaning the 02 sensor if you don't want to buy one, there are videos on yt on how to clean an 02 sensor, of course its better to buy one but your gutted cats may be causing issues screwing up your signals and damaging your sensors, maybe, not sure... But the good thing is you have good compression and a non-interference engine I believe so if you pop that belt still should be fine just have to align the new belt on install. Fundamentally you have good even compression and that's a big deal so that's great.

 

First, "Tubular" dude.

Are you using a Timing Belt purchased from Lexus or Toyota?

Have you checked the MAF sensor?

What condition are rubber intake, vacuum and emission components?

 

i would also check the MAF (but don't clean it with MAF cleaner - it's a karmen vortex which is sensitive to cleaners).
if that doesn't pan out check your timing.
i'm not sure how the 1UZ copes with gutted cats so that might be a trouble spot as well.