M30 Afm Fix No More Hesitation

[clhorton]

I was bored and decided to open my afm and found that the spring that holds puts pressure on the panel that opens with airflow was really loose. I loosened the screw on the side of the wheel that torques the spring and turned it to tighten it. The car has never ran better. In trying to solve that problem I pretty much did a complete tune up on the car oh well at least it runs top notch now.

[stu1]

It's great when you find something positively wrong - a nice feeling of achievement!

[genphreak]

I was bored and decided to open my afm and found that the spring that holds puts pressure on the panel that opens with airflow was really loose. I loosened the screw on the side of the wheel that torques the spring and turned it to tighten it. The car has never ran better. In trying to solve that problem I pretty much did a complete tune up on the car oh well at least it runs top notch now.

The immediate effect is to richen the fuel mixture. The ECU will learn however and this right-foot feel improvement will subside... watch your consumption for clues. In effect the ECU is being told it has more air than it is actually passing through the meter. Emissions are also affected. I did this by 3 notches, then 2. Now I am back to normal Same feel can be felt through a 'Shogun reset', although that subsides also as the ECU works out how to clean up the combustion process.

[alpinaracerX]

how did you do this??? i cant figure out how to get the damned thing open!

[alpinaracerX]

nvm got it open, tried to adjust it, didnt work.. still running like crap

[bill g]

Genphreak - clhorton has tightened that spring, which I reckon would lean the fuel mixture, although as you say the adaptive circuitry would trim the mixture back.
However the airflow meter is a load sensor - its input is also used by the ECU to set ignition timing. As timing is usually taken out as load (not RPM) increases and vice versa, tightening the spring would possibly increase timing advance which could be a reason for sustained improvement in performance at low loads (not full throttle), depending on fuel octane used.
I have tested different spring settings and found that tightening it does seem to give better performance at low loads like half throttle, but reduces performance at full throttle where the slower opening vane or flap is impeding the air flow more than it usually does. I have also found the opposite to be true - loosening the spring can help WOT and throttle response a little but reduces performance in other parts the operating range.
Of course if the spring just happens to be really loose and out of spec due to age and wear or previous tampering then tightening it really would improve the running regardless of all the above.

Bill G

[genphreak]

Good insights Bill, I agree- when I cranked mine up 3 notches to a harder setting it was better off the mark but WOT was not as good, I noticed that too. IN terms of rich or lean, I dunno, the damn AFM shits me to be frank- mine is to be replaced by a MAP sensor soon. ANyone that messes with teh AFM be warned, unless it is faulty you will just be screwing it up as it doesn't open cleanly, does not like humidit yand dirt and some say the silicone used to seal it has to be special. Flat spots are the only reason to do so, in most cases it si so critical to your fuel efficiency it is best to get a remanufactured one as the internal parts are not available... bah PITA AFMs... thanks Bill... good info re the timing advance you suggested the ECU would do.

[clhorton]

I agree that I feel a difference at WOT, but not having that damn hesitation anymore is worth it to me at this point. I'm a poor college student so it does the job for now, but I do want to just get a new unit to get it completely back to spec.