Thread: weird ltft at idle

If I let the car idle for more then 5 minutes the ltft's go -22.0 but they start at -0.7 for the first few minutes. As soon as you step on the throttle it stumbles and wants to stall. If you rev it up before hand and then your fine. The rest of the day it never happens again. I'm leaning towards a evap issue since everything else has been changed or swapped. Happened before my N* swap and after too fyi

Fuel pressure regulator going bad maybe allowing to much fuel in? I'd think a vacuum leak anywhere in your system would cause a +* LTFT since there is unmetered air entering you system casing it to run lean making the PCM add fuel, but if there's a vacuum leak around your FPR it could be showing less vacuum causing it to run rich. (thinking out loud seeing that since you lose vacuum once throttle is applied and more fuel is added) You are having rich conditions causing the PCM to remove fuel...

I could be complete wrong, I hope others chime in, but I'd check your fuel pressure at the rail to see what you are getting. I forgot if the Schrader valve is located pre or post FPR though, I think post. If you have proper pressure, could be an injector stuck open?

Injectors are flow tested and cleaned, fpr is replaced, good pressure and all new vac lines. The rich condition only exists on cold starts if I let it idle long. I'm not 100% sure but looks like my DHP tuner might be the issue. Sent it in for testing and it came back with data drop. It was tested sending 512kb though the tuner and sometimes it would spit out 512kb, or sometime it would 1-6 kb's. So I'm waiting for it to get repaired and flash to see if this weird issue just disappears.

What's your EGR and EVAP status? I was told once that the highest the PCM can command is +/- 16. If it goes any higher then that it's something with emissions.

My egr was replaced because I had a small stumble off idle about 4 months ago. Evap system is the only thing I haven't touched yet and I agree that the evap is a possibility. But after finding out my dhp box was bad I'm going to wait till I get it back repaired and flash it before I go tearing into the evap system, just to make sure it's not a bad flash causing it.