Hey yall,

I'm trying to figure out how to solve my fuel trim issues. Both sides are measuring 25% ST, -25% LT.

Previously, my LT trims were 10%, so I tried diagnosing with a smoke test, which I think damaged my MAF. I replaced my MAF with a Bosch from Rock Auto, and both upstream O2 sensors with NTK sensors, but I'm still getting these ridiculous fuel trims. I'm out of ideas and I don't trust Claude to diagnose further.

Both voltages for the front O2 sensors BEFORE and AFTER replacement, read 0.03 or 0.02v, which tells me this must be some sort of electrical issue. What should I be looking at next?

 

Get a scanner or obd2 bluetooth dongle where you can watch analog voltages, not digital. We want to see the curves plotted on a chart. You did not mention highway vs idle. Idle maxed can be a vac leak, especially if highway trims are reasonable. Highway trims way off means you have a massive issue - bad injector (unlikely), bad maf (unlikely), plugged converter (unlikely). Have you unplugged the maf and checked them?

 

Thanks for responding this one is really hurting my confidence in the D2. When you say “checked them” what do you mean by them? Trims without the MAF plugged in? What is “idle maxed”?

I haven’t driven it highway because I didn’t want to damage my cats from the excess fuel, which I can smell because the exhaust stinks.

I’ll get highway reading shortly and post back with graphs of idle and highway.

 

OK it's resolved! I just had to go out and drive it I guess the ECU had to re-adjust, and I didn't realize I needed to let the engine fully warm. After about 5 mins of driving, the sensor voltages started oscillating as normal, and after 20 minutes the LT fuel trims on both sides settled to -3% then to around 0%.

Man the D2 really freaks me out sometimes.