I posted this on 'tuners as well. Just trying to get as much input as I can:


Recently, out of no where, I've been experiencing a problem where all of a sudden my car will run extremely lean under WOT for about a minute, then return back to normal. I have a Zeitronix Zt-2 on my dash with a warning light/buzzer that warns me when I run leaner than 11.5:1 at greater than 10psi of boost. I'll be driving and go to accelerate and the light goes off. I look at my Zt-2 and the AFR stops solid at 13.0:1 AFR and will not go any richer, no matter what the TP or load is. A minute or so later, the problem goes away. This problem appears about once or twice in a 30-40 minute drive.

When its stuck in the lean condition, it reminds me of when the vacuum line pops of the FPR and your fuel pressure doesn't raise with boost...but, since the problem is intermittent, it makes me wonder if I have a malfunctioning FPR solenoid that is cutting off the boost signal to the FPR (or a faulty ECU that is triggering it at random times).

Any ideas? Where should I even start to troubleshoot? I might pull the vacuum lines from the FPR solenoid and loop them to see if the problem persists...


FYI, I'm running a rewired walbro 190 with stock fuel lines/filter/rail/fpr and 660 injectors tuned with the Ostrich/TunerPro setup. I have a fuel pressure gauge, but its under hood so I can't see it while driving. If you think it would help, I'll plug in the data logger and hope the condition reappears while I'm logging and then I'll post the log.

bypass that solenoid. Its not really needed. All it does is cut vacuum to the fpr during startup to bump up fuel pressure.

Yeah, I want to, but in the spirit of what we like to do here, I want to find the root of the cause rather than use a band aid. I'm going to bypass the solenoid tonight to see if the problem disappears, and then go from there to try and find the root cause.

Im pretty sure the circuit is strait from ecu. That solenoid is a NC solenoid (i believe) and the ecu power it up to open it. If it is a NC solenoid then, there is an issue with power or ground on the solenoid, causing power to intermitantly cut out and in, opening and closing the solenoid.