My 1j has an issue running rich, throws no codes. Mods to fuel system are 440cc injectors, single walbro switched to 12 volts, AEM AFPR with neo. Car had been running months before and recently threw a code 31 which I tracked down and repaired. What happens is the engine will crank over and fire fine and just then the afr's will go from 13ish and drop on the wideband to below 11 and bounce around a bit. I had caps replaced in ecu, changed out ecu's to check and I'm confused. The engine runs rich and I am out of avenues to check. what do you guys think?

 

vacuum leaks? leaking bov? injector stuck open...how does it idle? any smoke? does it rev up smoothly?

 

couple of things when i was getting mine wired right a few things were making it run rich. Main thing was a bad coolant temp sensor, although it had trouble firing when cold so that's unlikely your problem. I would look into the stock O2 sensor next.

 

Thought about it a bit myself and suspecting injectors to be stuck open makes sense. increase in fuel pressure didnt have any effect and no matter what ammount of fuel i pull on the neo it doesnt change the afr's. Not to mention that it doesn't throw any codes.