refuerzob

Hi all,

Not too long ago, my car's been going lean right before hitting boost (10inHg->5inHg). It increases from 14->15->16->17 AFR at this range. I've noticed that when the O2 sensor is unplugged, the car runs perfectly fine (AFRs don't increase incrementally as noted earlier).

I believe there are no vacuum leaks either since all the clamps are tightened down. I bought a new O2 sensor from a 300ZX in hopes of solving this issue, but the problem still remains. Someone locally told me that my 63 ECU (auto) could be the culprit since the fat O2 sensors from the 300ZX and later SR20DETs equipped with the fat O2 sensors send different signals (compared to the early model SR20DETs with the skinny O2 sensor). Oddly enough, the car was running just fine since October last year. Also, I've noticed the problem becoming a lot worse when the car gets up to temperature. At around 100F coolant temp, the AFRs go up to mid 15s right before boost. So far, I'm speculating a vacuum leak (although unlikely), replacing my 63 ECU with an E5 ECU, a short or pinched line in the O2 sensor wires, or getting a new elbow with a skinny O2 sensor.

Any insight on this issue is greatly appreciated, thanks!