SCShawn

iTrader: (2)

Hello everyone I just recently swapped my 1jz into my vehicle and came across this problem when I first started it up. It would run terribly rich, so rich that it would foul the plugs and then start misfiring, and then it wouldnt start at all after that because the plugs would be so black.
I read and read through so many threads and what pissed me off the most was when the person finally figured out the problem with the car, they never posted what was actually wrong with it.
Well here were some of the steps that I went through so if you do run into this problem, here are some steps to narrow it down.

1. At first I was convinced it was the TPS so I adjusted it maybe 4 times, and I ended up buying another one brand new.
2. Bad ecu, I cracked mine open, and honestly it was the cleanest ecu ive ever seen, so i scratched that one out.
3. Checked for vacuum leaks all over the intake manifold. literally everywhere, mani to p/s, mani to map, mani to bov. Did this by spraying some carb cleaner on the lines and listened to see if the idle jumped.
4. Changed the engine coolant temp sensor. This is the sensor that the ecu reads it should be green. When these go bad, it will throw the computer into closed loop mode.
5. Checked my coil packs for any cracks. There were none.

6. Then finally changed my O2 Sensor. This fixed my problem! I had to drive it around for a little to get it to re learn itself, but it runs perfect now. For reference I used the Bosch 13910 Sensor, this is the 3 wire O2 and uses the same flange as the oem.

If this helps just one person, then that is all that matters. I was really struggling for a while figuring out what to do with the car.
Cheers guys.

LoveSCs

iTrader: (2)

glad you figured it out, thanks for sharing

SC400slide

iTrader: (11)

It should be in the "SC Doctrine" that SC's (Lexus more-less) eat through o2 sensors like candy. Thanks for posting your findings.