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Re: AFM Question (archive)
[ Follow Ups ] [ M5 (E28) Message Board ] [ Msg. Board FAQ ]
Posted by Todd Kenyon on June 23, 2002 at 12:23:27:

In Reply to: AFM Question posted by Philo on June 22, 2002 at 01:13:24:

Although i've seen some things that say it's supposed to be smooth, in my experience they are not. Yours sounds similar to mine. If you look at the circuit board in there, you can see why it might go in a step pattern. I think the only red flag when doing this is if resistance suddenly goes to zero or very high somewhere along the track. Swap an AFM if you want to confirm. If your fuel pressure and vacuum leaks check ok, maybe pull the injectors and have them cleaned. Can't hurt, other than the $150 dent in you wallet.


Ive been chassing a hesitation and decided to full the AFM and test it. I know I didn't ha ve to pull it but i wanted to pull the air filter and it's just easier to yank the whole AFM and air box out. Anyway, I put the AFM on the ohm meter and here's what I got for a reading.

Oh yes, I know nothing about electronics so bare with me.

With the ohm meter on pins 4&2
* Closed gate = 0.2 ohms
* As I open the gate just off closed position it bounces slightly .01 ohm to .04 ohms.
* As I open it some more, about 1/4 open gate it runs up quikly to 1.2 ohms.
* From 1/4 to 3/4 gate it varies between 1.2 and 1.4 ohms.
* As I approach WOT it ramps up suddenly to 1.8 ohms.
* Then just before it hits the WOT stop the ohms drop back to 1.8 ohms.

Now I'm not a master tech but as I was opening the gate and watching the ohm meter I felt as though I was witnessing the hesitation when applying throttle but only on an ohm meter.

Can anyone tell me what the curve or reading should look like as the AFM gate is opened. Maybe it's time to drive over to Armando's house..., I'm buying the beer Armando,don't worry !

If the AFM checks out I guess I'll start looking at fuel pressure, vacuum pressure, leaks and so on. Wish I was a master tech in my past life.

So should the AFM curve be smooth and progreesive or should it jump to specific readings at specific gate openning points ?

Philo.




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