One of those, a friend of mine threads, but this one's real.
My buddy bought an 92 SC400 w/ 172k miles. Did a tune up - rotor buttons, distributor caps, wires, plugs, etc... Runs REALLY sluggish (like everyone else's, I guess). Well, did some research on here and saw a few posts about disconnecting the MAF.
When he disconnects the MAF, it runs like a scalded dog and throws the CEL (of course)

With the MAF connected, it's a slug. Throws CEL that are not stored in memory (??????). Replaced the MAF (used ones) and still the same problem.

Two questions, what is the original part number for the MAF on the 92 SC400 and what the hell does running great without the MAF mean? Thought it was that the MAF was bad, but got 2 of them - could both of them be junk or the wrong ones??

 

Try jumping the fuel ecu (search, i would tell you but i forgot how to do it). If it runs better, then you need a new fuel ecu.

 

could be bad MAF, though I don't suspect three bad ones, possibly incorrect ones though. Could also be bad throttle position sensor or a dead upstream oxygen sensor...

time to get out the volt meter and test for reference signals...

 

did you happen to change the ignition coil, sounds like the same problem my father had with his 92 ls400 a few years ago, he changed everything, wires, sparks, distributor cap and rotor, and also went threw 2 MAFS, went to Lexus and they did a diagonistic test, found out it was the ignition coil. put a new one in and the car was like new.

 

similar problem. car misfires with maf only in closed loop. I suspect o2 sensors.

 

Thanks everyone. Looks like a busy night...