AFM Adjustment Screw

[PG325]

I'm slowly getting my 1989 325i ready for its MOT, and the emissions were relatively high at the last one, I believe 2.22% CO and 212ppm HC.

The oil smells of petrol and I'm guessing this is because for the last 2 years the car hasn't moved and has only had it started every few months to keeps things ticking over.

I've checked the AFM screw and it is 17.8mm from the top, and I've read somewhere that the depth of the screw is written on the AFM somewhere, does anyone know where, as I believe mine may have been alterted over the years, certainly the red screw cap is missing!

[tha881]

I couldnt see mine either, until I cleaned the casing with a wire brush drill attachment, it is there, it probably just needs a good clean

[paultv]

Usually the setting stamped is no longer relevant...so much wear and fiddling has made it less important.

Best way is to visit your mot or garage guys and put a gas tester on it and set the CO to between 0.8 and 1.0 for a 325i.

Set and never touch it again....

This assuming there are NO air leaks and the AFM is clean as well as the ICV operating correctly, clean injectors good HT lines and distributor cap is in good shape as well as correct fuel pressure.

Paul

[PG325]

I have a Gunson gas tester, so will reset.

I assume that's at idle at no a certain RPM.

Do these age of cars even have a raised idle MOT emissions check?

[paultv]

The ICV controls idle through ECU...no manual adjust, no raised idle. Incorrect idle ie above 750-780 rpm usually result of air leakes, rough idle comes from injectors, plugs and vacuum leaks such as rocker filler cap seal, breather pipe as well as dip stick O ring and throttle body/manifold and brake servo pipes fittings.

Paul