Carrera 84-89 Air Flow Meter

indigowhale · 09-28-2004, 01:47 PM

So I took out my AFM to determine if it was causing bucking and hesitating below 3000 RPM on my 84 Carrera, as it turns out the voltage was going up smoothly then 0 then back to where it should be. Same thing on the way down, just for a second or so, same spot. Otherwise the potentiometer dials up correctly.

Moved the wiper, cleaned tracks, moved it again to new surface, same results.

Is this normal or indicative of a permanet problem? If so, does anyone have an AFM they want to part with? Only solution I see is replacing the thick film resistor board or get a used AFM.

Thanks

Indigowhale Fatman

Tim Polzin · 09-28-2004, 03:07 PM

That jumping around may be ok. FR Wilks has a pretty good description of the AFM and testing procedures here: (on lhe left side, Air-Flow Meter, AFM)

http://frwilk.com/944dme/

It is for a 944, but I think the function and design is very similar to the 911.

Tim

indigowhale · 09-28-2004, 04:51 PM

Thanks Tim,

According to Mr Wilk, my drop in voltage may indicate that it is bad. I am trying to confirm that, the drop lasts a fraction of a second but it is registered by the Fluke and I am sure by the DME.

kqw · 09-28-2004, 05:42 PM

Question?

Does the door swing freely? Warped?..... Have a major backfire lately? How about the sensor that is encased in plastic on the inside of the intake?

I can't believe that AFM 's are going bad.

My opinion..I don't think it's the AFM...Keep us updated

ausgezeichnet · ausgezeichnet's Garage

I also have an 84. How did you remove the AFM. It does not look intuitve on the Airbox side. Thanks.

indigowhale · 09-28-2004, 05:57 PM

The AFM is very easy to take off.

Remove the clamp on the left side, then 4 10mm bolts inside the air filter box and AFM mounting bolt and harness. It should take you about 20 minutes tops. The air filter will have to come off but not the other filter half.

Hard thing is taking the black cover off, I had to use a vice being careful not to crack it. Remove the silicon first, it is glued on.

All the internals and externals are OK, the box is damage free. The problem is with the circuit board and I don't think to many folks test these things on the bench. However, the symptoms that I think it generates are very common with the Carreras:
Backfire, bucking, hesitating. One thing to note, they seem to occur at a certain RPM range under 3000. My dead spots just happend to be in this range.

Coincidence?

Can someone who's bench tested a good AFM clear things up?