500RWHP FD Running Lean (11.8afr@24psi on pump gas) all of a sudden. Motor Survives!!
 

Hey guys, need some Ideas here. Been running well for the past year on this current setup.

Street Ported 13Brew
Haltech E8 ECU
BW s366 .91 (24psi)
1000/1600 fuel injectors
dual Bosch 044 pumps
3.5" exhaust
FMIC

Data logs run every time I drive the car, and this includes fuel pressure. All of a sudden on one of my outings with the car, I am seeing lean conditions right through each boosted pull. On that same outing the first few pulls were fine, but then the all became leaner by .5 - 1afr. WTF? There was no difference on the Fuel coensation tables. I have since driven the car another day to verify that it was not just a one off situation, but the problem persists. I do not want to blow the motor.

Nothing has changed on my tune and logged fuel pressure remaines the same as those on previous logs which have good AFRs. EGT's were about 45*F higher normal in the lean pulls, remains balanced between Front & Rear which would indicate that the problem is not just 1 injector.

I am leaning towards the ECU/software since the fuel system seems intact.

Has anyone ever experienced this?

Any Ideas?

I am leaning towards the ECU
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1993 R1 500 RWHP 25 psi BW S366 on Pump & Water

Wide band sensor going out? I've had to replace mine.

Check for an exhaust leak up stream of the O2 sensor. some air entering the exhaust stream will incorrectly read lean.

Also, 11.8 can work just fine, IF everything else is good. But running that "lean" leaves the engine vulnerable if a problem arises.