Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Good morning all, Helping a neighbor out here (or trying to not send him down the parts hole)??. Car has P0171 lean and has been to his shop twice. about 6 months ago they changed the MAF (Aftermarket) which he says solved problem for a few months. Happened again and he went back to this shop where they replaced both 02’s(aftermarket) and cleared code. He drove off and light back on! Came to me. Aftermarket MAF seems to report slightly low but did have a known good oem and swapped with no change in trims. LT is pegged at 27 - 29 and short term does not really make much correction. MAF hovers just under 2g/s with known good between 2 and 3 g/s. With known good no change in trims. Rear O2 is pegged rich. No vaccumn leak detected (water method only) will smoke soon. Trims slightly improve under load, but not much. LT to about 11 and short term moves a little. Im reading through the Danner Book? but trying to wrap head around the lean condtiion with pegged rich rear o2. Could I be dealing with bad new parts? Thanks community
so the LTFT will go from 25-29% at idle RPMS (what RPM?) to 11% under throttle (also what RPM?)
At first glance this bit of information does indicate a vacuum leak. or potentially a fuel delivery/pressure issue. the rpms you're seeing this at could help give a better picture
Thank you for reply, I actually just did a better data recording test drive and at WOT LT drops and ST raises and fluctuates making me thing fuel. I will attach screenshots of graphed data so you can observe as well
