The car is having some bugs to be figured out. Here is the very first one ...

Car starts and idles fine (AFR at 12), however after I give it throttle, the idle and AFR would become unstable and leaner to what it is mapped, today it get to a point that the AFR jumps over 16+ . It wonders between good and bad, the day before yesterday it ran total fine. It is ok when it's reved up and boosts fine but in general gets leaner and unstable after the symptom starts. I just put in a Koyo with a efan, and the temperature never gets past quart scale.

Here is a little about the car ...

GXL/TII conversion. BNR stage 3. 720 primary and 860 secondary injectors. S4 ECU with Rtek1.7 + SAFC. Port out throttle body. Carter 255 fuel pump. The SAFC is connected to boost sensor instead of TPS and was running fine.

I have checked the TPS using the resistance method and tried to fix a vacuum leak about the Greddy elbow to the throttle body (may still leak).

Here is a shot of the engine bay. She totally worth it!!! Please feel free to chime in before I tear things apart once again. If there anything in the engine bay that doesn't seem right (say that cap on the koyo overflow port), feel free to let me know.

-X

 

Oh, somehow I feel the problem may be also depends on the temperature, as it seems more vulnerable to the issue when it warms up.