System 1 bank too lean? MAF sensor bad or what else can cause this?

Asked by Jan 10, 2012 at 08:01 PM

Question type: Maintenance & Repair

My wifes car will not run.  I had it scanned at Autozone.  If you unplug the MAF the car runs fine.  I put a reman MAF in place of the OEM and the car still wont run. To date I've replaced the battery, plugs, air filter, PCV valve and changed the oil(it was due).  I have also cleaned the IAC valve and the injectors.  Took off the resinator and stuck a bar through the CAT converter(it wasnt plugged).  Since the reman MAF didnt help I took it back and got a can of MAF cleaner to clean the OEM one...that didnt help either.  Anyone have any insite for me?  All this started with a drained battery due to park lights left on overnight....

2 Answers


The Mass air flow sensor wouldn't throw a code like that. It's coming from one of the O2 sensors. It can only be one of two things. Either you have a vacuum leak leaning the fuel mixture with air the car doesn't see entering the engine. Or you have a problem not getting enough fuel to bank 1. Could be a clogged injector or fuel rail. It's gonna take some diagnostics not something most people can figure out at home.


A bad MAF sensor can cause a lean bank 1 code. I've seen it today actually. Placed a rebuilt MAF sensor in a 3.8L Camaro and bam! Lean bank 1 code came on, idle was rough, car almost died. Took it out, placed a MAF sensor I had which I knew worked & code cleared, idle was perfect, no hesitation.

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