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Taking the advice of ZZPerformance, I removed my AEM fuel pressure regulator and re-installed my factory regulator. The engine now starts instantly ( took 3 or 4 seconds with the AEM regulator), but my fuel trims have spiked to -18. What has happened?
The car is a 2000 GTP.
Do you know what your AEM fuel pressure regulator was set at? The stock regulator is 48-55 so if it got tuned at 40psi you are now injecting too much fuel.
Is the factory regulator keeping it at the same pressure or allowing more fuel pressure?
If it's more, I could see the higher negative trims because more pressure means more fuel will be going through the injector when it opens.
AEM was set a 54 psi---supposedly!! Perhaps it was reading 54 at idle, but was actually lower! I have adjusted my LTFT's and now the car starts instantly, where before it took at least 2 to 3 seconds.
Update to this post. The last few times that I have scanned the car, my fuel trims go lean, 6 to 7 to 8, under medium throttle at about 6500 mhz. I have no KR, but I know running extremely lean can damage the engine. Fuel pressure at idle is 48 psi. Didn't change after installing new pressure regulator. I think my fuel pump is failing to go into high speed mode. Replaced both of the fuel pump relays, no change. Attached a couple of scans. What do you think?
Can't look at your scan right now, but have u checked for any exhaust leaks pre O2 sensor? I had a leak at the crossover and it made me lean up till boost, then it was fine over 7000hz