AFM testing

[sigkadetm]

I think I may have a bad AFM. Tested and found the following readings:
Terminals 6&8 365 ohms
Terminals 7&8 375 ohms
Terminals 8&9 350 ohms

I have a 1980 spider. Seems to run well but not when first starting up. Then its fine when warmed up. Did the modification on the AFM and it seemed to help a bit. The air bypass screw is out 1-1/2 turns. Checked the O2 sensor and it reads 425 to 441mv. Any suggestions would be appreciated.

[GeorgeT]

I would check the Coolant Temperature Sensor and then the Auxiliary Air Valve before working on the AFM.

[KevAndAndi]

What modification did you do to the AFM?

The air bypass screw is not really an owner-serviceable item. That's why it's supposed to be plugged to prevent tampering.

I've been a broken record on this topic, but here goes, once again: If you're having trouble with your AFM, and it has not already been refurbished, send it to Fuel Injection Corp. or a similar firm and have it refurbished. The work done by FIC on my AFM transformed the car from an overly rich situation with wildly varying idle speeds and frequent stalls to running like a top. I still have some work to do, but the AFM refresh was by far the most important element, and it has been the best $200 or so I have spent on the car. (The price included replacement of electronic components, testing, and blasting and painting - it looks like new.)

Mine was an extreme case. The air bypass screw had been fiddled with, the fuel pump actuation arm had been bent, and the air flap was not working; in fact, it was bent outward, so the AFM was not fulfilling its primary function at all. I also suspect that the wiper track inside was badly worn.

[sigkadetm]

I installed the wire on the arm and repositioned the wiper track. Cleaned all contact surfaces too. Maybe needs fine tuning. Looks like it is running a bit on the lean side. I guess I need to get a gas analyzer and make sure the air bypass screw is adjusted right or maybe the tension is not right on the flap.

[sigkadetm]

Like to know where they got electrical components for the AFM. A new swipe board would be great!!!

[KevAndAndi]

I installed the wire on the arm and repositioned the wiper track. Cleaned all contact surfaces too. Maybe needs fine tuning. Looks like it is running a bit on the lean side. I guess I need to get a gas analyzer and make sure the air bypass screw is adjusted right or maybe the tension is not right on the flap.

If you can adjust the air bypass using a gas analyzer on the car, I believe that is superior to the way mine was adjusted, by the refurbisher on the bench.

Sounds like you know what you're doing unlike many owners who mess with the AFM with no rhyme or reason. It's just not a job I enjoy or feel comfortable doing, so sending it out was the right choice for me. YMMV.

[KevAndAndi]

Like to know where they got electrical components for the AFM. A new swipe board would be great!!!

Yeah, apparently they have access to new components, but I have no idea what their source is.

[RRoller123]

I have asked this question a few times of various vendors, regarding whether the refurbishers replace the TFR board with a new one. I haven't been able to get a definitive answer yet. So, for me, all the other cleanups will do for the time being, and they have absolutely helped the car run a lot better.

I believe that I have read from multiple sources that this system is designed to purposely run a little lean from the factory, to help meet air pollution requirements back in the day.

[sigkadetm]

Cleaning and refurbishing has helped the idle but I still get like a sputter when engine is cold. As I accelerate.

[lglade]

As mentioned above, read up on your Auxiliary Air Valve (AAV); there are several good threads on this site. It's easy to remove and test and supposedly needs a good cleaning about every other year.

But it's well know for contributing to cold-running issues on FI equipped cars.