Stock ECU Fuel Trim Issue
 

Long story short, swapped a 00' JDM 1.8 into my 00' and using the factory ecu until I get my megasquirt configured for a NB (moving over from a 95') I'm seeing LTFT in the plus 20% range and STFT is pegged at -25%. Just trying guage the health of the motor until I get the MS2 on it. What would cause this? Currently the only codes are for the lack of a secondary O2 sensor.

So 125 views and no comments, I know this is an odd question. Here's some more data to ponder on. The JDM motor has a BP5A intake cam (AKA MSM cam), it also has a tubular exhaust manifold that I'm using that is very similar to the 02+ cars. So everything points to this motor moving more air than the original motor, being that it's still a MAF car it shouldn't matter. Any kind of leak between the intake and the MAF would result in a lean condition not rich. I highly doubt I have a high fuel pressure issue so what else could cause a motor to run rich?

The only thing i can think of is that there was some salt induced corrosion on the exterior of the motor ( shipping in a crate on a boat I assume) so maybe the O2 sensor is fubar? The original O2 was exposed to a ton of oil burn so I wouldn't trust it either.

I couldn't care less but if there is an issue with the motor I don't want to waste time with the MS tuning around it. Have a DIYPNP MS2 and a WB that will eventually make it's way on to the car.

Sticking injector, vacuum leak, biased o2.


Negative trim means the car is pulling fuel. If it drives normally, no misses, I'd be looking at the O2.

Did you clear the trims when you installed the engine?

How would one go about this? A simple power cycle do it?

Obd2 scanner will do it. You currently have a +5% fuel trim, sounds like it'll even itself out eventually. with a new engine you need to start zerod out though, not with the long term trims from the old engine.