Air Flow Meter

[catandsplat]

Hi All,

Just a general query. I squeezed the car through the mot (or rather the garage did by tweaking the AFM to get the right co2) but it's now gone off tune slightly. Usually this is cured by re-setting the
AFM on the analyser. Obviously my AFM is on the way out.

Does anyone know if there's a modern electronic replacement which
can replace it, or will I just end up with a newer model of the old
AFM?

Cheers,
Chris
92 Griff BV

[2 sheds]

I would get the car set up by Mark Adams he has a rolling road session at Austec in crawley twice a month, Austec also have some second hand meters,
Tim

[steve-v8s]

Is your car a Pre Cat engine ? I had real problems getting my 92 V8s CO to MOT values. The CO was fine in cruse and the car ran very well but it was simply too rich at tick over. Checked all the sensors, tried a different AFM and ECU, replaced the pressure regulator, even consulted Mark but never sussed it. The routine for MOT was simply to remove the bypass hose (goes to the stepper motor driven by pass port) and replace it with a hose fitted with a heating system drain trap. You can then open the tap to effectively introduce a controlled air leak and lean up the mixture. When you have the ticket pop the old hose back.

[griffter]

How do you tweek the AFM? I can't see any adjustment on mine (pre-cat).

[steve-v8s]

Hex headed adjuster a long way down a hole in the side.

[catandsplat]

Hi

Yes, it is pre-cat. The adjuster must get worn in the one position and just doesn't stay put. Any major bump or twist (unavoidable pot hole etc) and you immediately hear the difference. Goes from instantly pulling hard in fourth at low speed to a brief pause before setting off. Also makes engine sound lumpy at idle and pops'n'bangs on overrun. Sounds good actually but not ideal!

Chris

[steve-v8s]

That sounds more like a problem with the throttle pot than the AFM to me. The track becomes worn in one place. Try connecting a voltmeter to the slider and see if you get a nice smooth change in voltage over the entire range. A proper meter is better for this than a nasty digital one.

[catandsplat]

I have checked it in the past and it tested ok. It didn't seem to dirty when I last cleaned it up, maybe it's time for a new one just in case?

Chris

[HarryW]

You can actually measure the value of the AFM pot, can't remember which wires though, but can't be difficult as there are only 4 (I think) to it. Seem to remmber approximate values of 1.4V for cat car and 1.8 for pre cat, or it could be the other way around.

Harry