What if I have normal injectors and flex fuel tune?
04-18-2012, 01:40 AM
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What if I have normal injectors and flex fuel tune? 2003 5.3L/4L60E into 64 chevelle.
I think I may have found my trouble. I think I forgot to tell my mail order tuner that I was using normal injectors and not flex fuel injectors.
My trouble is long term fuel trims LTFT are running at or near +25% most of the time. Bank 1 is maxed most of the time, bank 2 is +10-25% and maxed some of the time. Car is running rough and very rich, the old oxygen sensors I replaced were covered with black soot, but car doesn't smoke.
I replaced oxygen sensors and got rid of my trouble codes for oxygen heaters malfunctioned. Now I am getting P0171, system too lean. I cannot find a vacuum leak and I have cleaned the MAF sensor and it appears to be reading correctly when I trend it.
I guess the PCM thinks there is excess O2 in the exhaust and keeps trying to add more fuel to compensate. If it thinks it has a flex fuel injector (bigger injector) then the PCM would call for a shorter pulse than needed for a normal injector. But since it is a normal injector it doesn't get as much fuel as it needs, so it is running lean and trys to increase the fuel trims to compensate.
Anyone think I am on the right track?
I think I may have found my trouble. I think I forgot to tell my mail order tuner that I was using normal injectors and not flex fuel injectors.
My trouble is long term fuel trims LTFT are running at or near +25% most of the time. Bank 1 is maxed most of the time, bank 2 is +10-25% and maxed some of the time. Car is running rough and very rich, the old oxygen sensors I replaced were covered with black soot, but car doesn't smoke.
I replaced oxygen sensors and got rid of my trouble codes for oxygen heaters malfunctioned. Now I am getting P0171, system too lean. I cannot find a vacuum leak and I have cleaned the MAF sensor and it appears to be reading correctly when I trend it.
I guess the PCM thinks there is excess O2 in the exhaust and keeps trying to add more fuel to compensate. If it thinks it has a flex fuel injector (bigger injector) then the PCM would call for a shorter pulse than needed for a normal injector. But since it is a normal injector it doesn't get as much fuel as it needs, so it is running lean and trys to increase the fuel trims to compensate.
Anyone think I am on the right track?
04-18-2012, 05:29 AM
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Your tune needs to match the injectors... Running a flex fuel tune with non-flex stock injectors will cause it to run lean. It is not rich if your LTFTs are +25%... it is very lean! If you basically have a stock non-flex fuel setup, the easiest way to fix it would be to full flash a non-flex OS into the PCM.
