I did a complete engine swap. Compression is 100%, car started on the first crank. However when idling, the afr is steadily beyond 17.5 but car doesn't feel like it's stalling or anything. Any suggestions? I made sure all the plumbing is correct and tight. So far I suspect a boost leak, but any other suggestions? Could it be a bad O2 sensor? Bad maf sensor? The short term and long term used is beyond 12.5 for both at idle but cruising is also a bit lean, not as bad though. Thanks

 

If everything else seems to check out just fine, use a different wideband O2 sensor to confirm your findings. Don't replace the one you have installed, just use a known working sensor from another enthusiast or spare you may have.

 

Throwing any codes at all? Check your sensors, seems like its getting a weird reading somewhere and trying to compensate for that. And as said above of course see if your wideband may be wonky.

 

Location of the o2 sensor ?

 

If it's maxing out the fuel trims positive, I would say you might want to believe the wideband.

OEM fuel pump? OEM FPR?

 

Are you using the same injectors before and after the engine swap?

 

I was reviewing my ROM today and noticed that idle ignition timing is advanced, it's aroud 10* instead of 5*, also idle timing compensation limt is set 3 instead of 8. I guess those changes were to make idle more stable.

Could it be the cause of lean idle? if yes, how can I fix it or should I leave it like it is?
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