Per the FSM test procedure, I'm getting a resistance measurement between E2 and Vs of about 288 Ohm with the flapper door closed, but only 24 Ohm when the door is fully open. Specs call for 50-500 Ohm. Is this enough of a deviation from spec to suggest I need to replace it? There is also something small rattling around inside the AFM case.

My car is an '88 NA, low mileage (52,000) and everything is stock (except for a RB cat back). I'm having pretty severe low RPM hesitation and bogging. Car starts fine but idles roughly. Above 3500 RPM it feels normal. Last time I drove it for 20 minutes or so, I noticed the main cat and front of the Y-pipe were glowing. I have done a resistance test on the TPS and it appears fine. I know I have a lot more stuff to investigate and eliminate, especially looking for vacuum leaks and fuel delivery issues, but thought I'd start with the AFM.

When I bought the car 7 years ago, it had a K&N drop-in filter and it looked like the previous owner may have over-oiled it. There was a black tar-like goop inside the airbox which had seeped into the AFM. I cleaned it pretty thoroughly and carefully at the time, and the car has run great for years. Still, I wondered if the AFM had suffered some kind of long-term damage from the mystery goop.

Thanks for your suggestions.

-David

 

Here's another odd detail I just discovered. I originally tested the AFM in my garage where the ambient temperature was about 90 F. I brought it into my house and left it sitting on my washing machine while I made dinner. When I just looked again at the AFM, the flapper door had somehow crept past the natural stopping position and was extremely resistant to being pushed open. Once I pushed it open, it sprang back to what I assume is the normal closed position. However for the first few times I manipulated the door, about 2/3 of the way through its travel, there was an audible clicking sound as well as a little friction. Has the change in ambient temperature from 90 F to 70 F made a difference in its operation somehow?

I'm getting more of a feeling this AFM has some issues.

 

im sure satch will chime in soon, but just looking at the Specs it calls for and then your specs, its halved... i would saw theres an issue. but im not the most familiar with this. satch knows all lol

 

Sounds like you have oil contamination with the door on top of the resistance being out of spec. It's time to get a new unit.

 

Thanks for the replies.

I see Mazdatrix still stocks new Mazda OEM AFMs for the S4 NA, but they're $917! I wonder when the last time was that somebody bought one?

Is it wiser to get a remanufactured unit or to just find a working used one? My inclination is to spend the extra money for a reman one because it seems to me more likely that it will last vs. a used one of unproven condition.

I see that Rock Auto has two different brands of reman AFMs for my car: A-1 Cardone and Standard Motor Products. Both have a one year warranty, and they're within $25 of each other in price. Does anyone have any experience with either of them?

 

The remanufactured units are usually just cleaned and polished versions which often don't work worth a darn so you are much better off and buying a used one from a member of this site.

 

I called Ray Crowe at Malloy just out of curiosity and he says the N326 AFM is now NLA. I suppose the Mazdatrix site may not be up-to-date on this. I guess I'll be hunting for a used one then.

Thanks again, everybody.

 

mazdatrix has there own supply i thought? but like satch said grab a used one from here. also worth asking if the seller is willing to get a video of it running with that AFM