I have a lean code P0171 that I've been chasing for 20k miles off and on. The car is a 2012 Honda CR-Z EX automatic with 99k odo. It has a heat-shielded Takeda CAI and a split exhaust that it has been tuned for, however my long term fuel trim in the 29s.
I have tried testing/cleaning the MAF, full fuel system cleaning service, replaced spark plugs, PCV valve has been replaced.
Code comes and goes as the wind blows. Stuttering acceleration, and slight engine knock below 10-15mph has been consistent. Code only pings when stuck at a light/traffic with ac/heat running. Never at highway speeds.
I have owned the car since 42k miles with all of the mods equiped, so I assume it's not a tuning issue.
Thank you for any and all help on the matter!
Rev up your engines!
The kind of modifications you describe can do only one thing to sophisticated computer controlled cars - screw them up. You need an expert automotive computer programmer ($$$$$) to make whatever adjustments are possible. Yes, a vacuum leak can cause stuttering and a whole lot of other problems.
