I was testing the afm on my S5 T2. I was doing the first test in the FSM, it tests the potentiometer circuit. It has a resistance spec for when it is open and when it was closed. My afm was with in specifications. However, when you slowly open it up from the closed position the resistance jumps around quite erratically. For example, in the full closed position it reads 250 ohms, if you very slowly start opening it the resistance will go up 450 then 500, but then it will drop down to 350. Keep pushing it some more and it will get to 650 ohms and then it will get back to 350 ohms again. I have always heard that a potentiometer is supposed to be a smooth incline when you open it, but it doesn’t say anything about it in the FSM. So does anybody know if this is normal or is my AFM shot? By the way, I was using a DMM, I do not have access to an oscilloscope. Thanks....

 

Nobody has any expierence with this? The problem i am having is that it bogs reallyh badly on acceleration. Any help would be appreciated.

 

Well first of, the FSM test is a bit confusing. it gives quite a range of tolerance, unless i am reading it wrong.
but the resistance should be decreasing as the AFM opens more. it may not be a perfectly linear response, but it shouldn't go back a forward by any large amount.

get a hold of a analog multimeter so you can see the "sweep" of the dial as you test.
it sounds like the AFM might be a bit defective and you are getting "dead spots" somewhere in the potentiometer range. you will be better able to see this with an analog multimeter.

this type of problem would cause fuel delivery issues. if this is the case, no way to fix it really, just get another AFM that works.

and you have probably done it already, but check the ECU for any error codes ("check engine light" method).