Hi, I am having idle problems, too rich and high revs.
Once engine warmed Temp needle at half, AFR 11.8 and 1,300 rpms
The rpms and afr only moves if I put some load at the engine, like releasing the clutch with a gear and brakes on.

I have replaced: (one by one and testing after each change)
New O2 sensor
Throttlebody (small leak from the seal)
IAC Valve.
Fuel pump, (walbro 255 for walbro 255)
Fuel Pump Relay.

MAF cleaned

And today testing the FPR (oem) once engine at working temperature, and I removed the vac line and blocked the leak, and there was no change, same revs and same afr as if connected. Only changed if I opened the vac line (more air). I put 20psi of vac to the fpr with a hand pump and no change.

Sadly I do not know how to test the fuel pressure, I am thinking about install an aftermarket fuel pressure regulator with a gauge.

2003 EVO VIII 40,000 miles
1000cc RC injectors
FP green
MAF (no SD)
Zeitronix AFR, BOOST, EGT
Walbro 255

Any help, advice or anything is well received, thank you very much. I am stuck at the tuning process.

 

Update.

Tested with my IX MAF, no change
with Oem fuel pump, no change

 

Honestly dude it sounds like the tune. Are you in the middle of the tuning process? Was the car previously tuned and finished? Also, depending on the weather (temp/humidity) the car will run a little richer or leaner depending on the difference between the day you got it tuned temps vs temps as we speak. Did this Come up all of a sudden?

 

The problem came when installed the FP green and the 1000cc injectors. The tuner says the car must have a fuel problem. (remote tune).

Very rare, I made almost the same changes to my IX (750cc RC and FP green) and the tuner made a fantastic tune with the car, no problems, and same conditions.

 

Did you ever figure this out? Sounds VERY similar to my situation.

 

TSCOMPTUNED..... done.

 

I changed from 1000cc to 750cc (RC both), the tuner made a tune for that change, and at the first ROM, the car is 14.7 at idle.