Lean condition
Thread Starter
Joined: Mar 2014
Posts: 699
Likes: 59
From: Alamogordo, NM
Lean condition I have a 2003 5.3 LM4 in my '39 Chevy and have been fighting a lean condition (codes P0171, P0174). The codes will set after a short drive and after closed loop. Once cleared they will not come back during that drive cycle but will reappear if allowed to cool down. Watching the short term fuel trims, they appear normal and run between -2 to +3 or so but all of a sudden will go nuts and set the code, then back to normal. MAP sensor reads 4.35 PSI at idle but I'm at 4300 feet. Replaced the O2 sensors but just realized that when I replaced them I used '03 sensors and have an '05 tune. Looking at Rock Auto I see the numbers for the '03 and '05 are different. Could this difference be causing my problem? Oh, no vacuum leaks that I can find.
Thread Starter
Joined: Mar 2014
Posts: 699
Likes: 59
From: Alamogordo, NM
Quick update, just looked at the long term fuel trim and one is at 23.9 and the other at 25%. How did they get there? Short term is cycling about -2 to + 3. What could be causing this?
