Trouble code 18

[Terry in Va Beach]

I unplugged the EFI fuze to reset the trouble codes and increasedthe idle by rotating the the throttle position sensor (TPS) clockwise. It now idles fine with no stalling. However, the cars is missing as I slowly accelerate as well as pinging at lower rpm especially during acceleration, so something is not right. I trhink it is still operating in the fail-safe mode. Trouble shooting according to the book, is first to replace the MAF. If that doesn't fix it (new part is $1000 so if anybody has a good used MAF for a 1990 LS400 for sale let me know?) It just seams that there arre no moving parts in the MAF to fail. There are a lot of sensors going into the ECU. Anybody have any ideas. Perhaps O2 sensors? (4 in all). Unlikey the majority of them failed but car is 15 years old with 175K miles and perhaps most had already failed.

 

[JeffHarper]

Why did you need to reset the fuse and move the throttle body in the 1st place? What were you trying to fix?

 

[Lextreme II]

18 is 2nd TPS.... check out these pages.
Engine Specs & Diagrams
Diagnostic with Codes
Diagnostic with Symptoms

 

[Terry in Va Beach]

Make that code 31

I just checked my sheet from the Lexus dealer and it was code 31. They said the first step was to replace the MAF so I am assuming they at least trouble shot it down to that point.