can anyone help i have a 1997 540i my check engine light is on, when i check the code using the reader i got from bavarian autosport it said "fuel trim, ql additive, CyL 1-4.
do anyone know what this means? thanks in advance..
I've had something similar, except the code in my case was "Mixture Control Off Idle". Believe this is telling you the computer has having trouble maintaing proper fuel/air mixture. This can be cause by a fuel supply, or fuel measurement problem. Fuel measurement is either the MAF or the pre-cat O2 sensors. A Vaccum leak or fuel pump/filter problem is also a remote possibility.
In my case the fault was set for both banks at the same time. As there is only 1 MAF (making it common to both banks) , it was my 1st place to look and indeed was the problem. I cleaned it using a cleaner specifically for MAF units made by CRC (Strauss Auto). It worked wonders. Not only did it clear the CEL, it solved the incosistent/wavering acceleration I was feeling. For me think what was happening is the system was alternating between using the MAF, and when things got out of range (because of it being dirtly), would switch to a default fuel calculation based on throttle position and O2 sensors. It was this switching back and forth that cause the wavering acceleration as well as setting the CEL.
In your case as it only set it for one bank, still could be the MAF, or possibly an aged O2 sensor (as they are bank specific), or yet something else.
One other point. On my car (MY 2000) I needed to get a Torx 20 'Security' bit to remove the MAF for cleaning. Make sure it's good and dry before you start the car (have read about people burning them out if not dry).
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