AFM adjustment to pass MOT

[JRoo]

Hi,

Help needed for a MOT pass on an 1990 E30 320i.
It is an ex PBMW E30 used as a track car. Unfortunately not been used the last year or so - but want to get it through the mot next week and running again.
Car has previously passed MOTs - but critically failed on CO (4.36%) - the garage told that like many PBMW E30 320i was running rich. So I had the AFM adjusted. Passed. And has been adjusted back (as it was running fine at prior setting).
Is the adjustment simply a few clockwise clicks on the AFM dial? If so how many would likely achieve the sufficiently lower CO reading?

Thanks for any pointers - I am no mechanic. But hopeful this is simple DIY job.

J

[JRoo]

Bump

[Brianmoooore]

MOT test is only concerned with CO levels at idle, and this is normally adjusted by the adjustable air bypass valve on the side of the AFM*. The more the bypass is opened, the less air there is opening the 'barn door', so the mixture is weakened. Above idle, the bypass has a much less proportional effect on the air opening the door, so has less effect on the mixture.
I've no idea if the bypass can flow enough to counteract the adjustment that's likely to have been done to the clock spring, but the best approach is to get the MOT tester to hook up to the gas tester immediately before the actual test, and adjust it then.
Alternatively, acquire an unmodified M20B20 AFM to fit just for the test.

* Don't adjust on an unmodified car. If gas ratios are wrong, then find the fault that's causing it.