Bad AFM? Fixes?
 

Hey, trying again to get emissions passing on my 1987 TII...
Took it to a repair shop, they claimed the computer was giving a bad AFM code, running rich, fouled O2 sensors and plugs. Compression is not great but not terrible (90-95 psi all faces).

I'm planning on taking the AFM out tonight and testing per FSM, but I was wondering: what is the cheapest way to fix the AFM if it's bad? Are the remanufactured parts offered online for ~200 bucks any good? Are there any vendors people have tried with good results? What's an affordable way to deal with a bad AFM?

Does anyone have any suggestions?

The cheapest way to get it fixed is to get one from a junk yard or someone online. After that, it involves the dealer and gets very expensive. They are highly calibrated and not easily serviced.

So, would you consider the aftermarket/remanufactured parts to be no good?

I'm still curious if anyone has bought one aftermarket and tried it--at $200 instead of $900, it might be worth the shot anyway. It only looks like it'll take half an hour to install anyway.

I'll post more after I've run the FSM test on the AFM.

Thanks for the reply, Sideways7.

hack if you are going to spend that much i have a backup AFM i will sell you for $100 lol

Look on the classifieds on this site. I just picked one up for $35 shipped. (as long as it gets to me). Just take a look.

Alright, here are the details of my FSM test on the AFM.

First off, the plate opens smoothly and with little resistance.
Second, I have measured the resistances as dictated by the FSM. Here are the results.

Pins tested/Resistance Measured/Resistance in FSM.

3-6/261 Ohms/200-600 Ohms
3-4/280 Ohms/200-400 Ohms
3-7/1.7kOhm/somewhere between 1.3k and 2k (between 20 and 40*C)
1-2/infinite/infinite

As I test the response of the opening plate,
1-2 opens suddenly after pushing plate about 1", closes again when plate closes.
3-6 goes from 270 Ohms fully closed to 40 Ohms fully open, but the resistance jumps around a bunch in between.

If the resistance is supposed to arc up like that, then the AFM works according to the FSM. I'll clean the terminals and put it back into the car.

However, it looks like the Air Bypass Adjust Screw on the outside of the AFM may have been tampered with. Does anyone know how to reset it?

Can somebody with some knowledge let me know if the 3-6 resistance is supposed to move randomly as I move the vane? I'll try a search, too.

I would be really appreciative if someone would drop in with some quantitative information.