AFM Air Flow Module Question

[RRoller123]

I am just starting to do the "wiper adjustment" on my AFM and have a couple of questions:

The inside of my AFM inside is gunked up a little from probably never being cleaned, and it is rubbing along the top when the plate gets about 2/3 fully open, and actually sticks on occasion. I am thinking that a good cleaning may be all it needs. Can I spray carb cleaner in there to flush all that gunk out? I assume that it won't hurt the module?



Also, the top cover looks to be just held on by some RTV silicone. Does this just simply come off by cutting around the bead? Any positioning pins etc; to watch out for?



Thanks!

[vandor]

I would clean it with a rag soaked with carb cleaner, so you do not get a bunch of carb cleaner inside the AFM.

Just cut the silicone around the top cover and it should come off.

[RRoller123]

Thanks for the guidance, I will give that a shot.

[divace73]

the air flap door may be warped if cleaning doesn't solve the sticking problem. To solve this problem you can
1. Get another working AFM
2. Try and lightly remove material in the area that is sticking (not my personal preference)
3. Remove the rivets from the base and remove the complete assembly , straighten the flap, then put back together, however you will have to drill and tap where the rivets were and also seal with some sort of silicone.

Option 1 is often the easiest and somewhat more cost effective as it can take a bit of time for 2 & 3.

[RRoller123]

Thanks, that is good advice. I think I will try some 400 grit or lighter sandpaper if the cleaning doesn't do the trick.

Here is the inside of my AFM. The worn tracks are clearly visible at the UL, 2 arrows, so I did the wiper mod which involves lowering the arm on the shaft, forcing the track contact points further out on the thick film ceramic. I found that loosening the bolt alone wasn't enough to let the arm move on the shaft, even with some reasonable pressure. I had to take the locking bolt fully out and put a small screwdriver in the area where I put an arrow and gently pry it apart. After that it slid easily down the shaft. I lowered it about 1/16" as advised earlier. Will follow up to see if this helps.



The cover has a channel all around it that seals the unit, I will fill it with silicone RTV and put it back on, but probably not until after I clean the airway, in case the inside needs to be subsequently cleaned. If anyone does this mod, be really gentle in prying off the cover, it is really easy to chew up the sealing lip. You can see a few areas where I had to get a small flat blade it there to pry it off.



One more thing I found which seems odd: There is an arm that swings with the wiper unit and it seems like it is supposed to make contact with another arm when closed (at rest) and cause an open in the circuit. In my AFM, this arm comes nowhere near the contact arm. Seems odd to me. Does anyone have any knowledge of this? I am not going to fiddle with it, but I am curious as to its purpose. Here is a picture:

[focodave]

RRoller,
I believe that little arm is supposed to operate the contact switch for the fuel pump. When the car is not running, the arm should open the contacts to the fuel pump to shut it off.
When you crank the engine over to start it, there is enough air flow through the AFM to actually open the flap enough to move the little arm, thus allowing the fuel pump contact to close and energize the fuel pump. Once the engine actually starts, the contact switch is in the fully closed position (because there is sufficient air flowing through the AFM to open the flap)to allow the fuel pump to be energized.
Dave

[vandor]

> I believe that little arm is supposed to operate the contact switch for the fuel pump.

Yes.

[RRoller123]

That makes complete sense, as the PO wired the Fuel Pump to be on all the time the ignition is on. I haven't changed it back yet, and I think I will just put an inertial safety switch in the trunk like donm did and leave it as it is. This explains why the arm looks to be bent so it won't contact the FP circuit breaker. It is bent!

Anyway, the AFM flap does look to be a little warped and was dragging at various points along the body of the casting. I looked at drilling out the rivets on the bottom to get at the warped arm and said no way. So I took it apart (mostly just to be sure I didn't break anything) and lightly sanded (400 grit) the areas in the air chamber where the flap was dragging. Worked slowly constantly cleaning and checking, and after about an hour I have it moving freely again. A good wipedown and a cleaning and light lube of the airflow chamber with PB Blaster and it is smooth as a baby's bottom now. I also put a single drop of 3-in-1 oil in the top at the point where the bearing is located that holds the wiper shaft.





The connector and top wiper come out easily as one piece. The contact area was badly pitted so I burnished it very slightly to hopefully make a little better contact. It seems to be nickle or hard silver plated so go easy on it if you do this.



I noticed that the shaft that the wiper rides on has some vertical play. I didn't see any way to adjust this, but the black disk that rides against the bearing in the casting looks to be pressed on, so I tried to set it a little deeper. Might have made a little difference, not sure.

I set the wiper down ~1/16" lower as recomended and put the unit back together, installed it to the car with the top still off, and tested it, and it is now running like the car is brand new! I can't believe what a difference all this made. Fixing the sticking flap as well as the new wiper rider track made a world of difference! It solved the stumbling completely. The power used to cut in and out, seemed like a fuel starvation/injector issue etc; but it was clearly the sticking AFM flap that was causing the problem. I would recommend this procedure to anyone, it was actually one of the easier things I have done on the car!



I put the cover on with some RTV silicone after making sure that the wiper moved freely and smoothly when the engine was revved.

One more thing, and this is odd..... The "chirping" sound that I have been trying to diagnose for awhile is gone. I noticed when handling the AFM before fixing it that the flap made a screech/chirp as it moved. The chirping may have been this all along, but I need to drive it some more to be sure.

Pete

[divace73]

just be sure the tension on the door flap is the same as it was, if not you will get either a richer or leaner condition.

The chirping sound may have been the metal to metal contact of the door flap, come to think of my car made the sound prior to as well.

[RRoller123]

Right, I didn't change the position of the wire clip that holds the wheel in position (the red circle in the picture below). I suppose you could mark it and fiddle with the tension on the spring by rotating it either CW or CCW to change the tension and see if it improves performance. I would think that lowering the tension would allow the flap to open more for a particular air flow and thereby enrich the mixture. Supposedly the lower tension would allow a little faster throttle response too, but I left it alone.

[RRoller123]

I am really hopeful that the damned chirping was because of this silly module! Wouldn't that be nice, a lot better than a transmission problem!

[divace73]

Right, I didn't change the position of the wire clip that holds the wheel in position (the red circle in the picture below). I suppose you could mark it and fiddle with the tension on the spring by rotating it either CW or CCW to change the tension and see if it improves performance. I would think that lowering the tension would allow the flap to open more for a particular air flow and thereby enrich the mixture. Supposedly the lower tension would allow a little faster throttle response too, but I left it alone.

that is the theory, I have reduced the tension on mine a bit, but really without measuring wouldn't really know....

[RRoller123]

A friend of mine with an X1/9 (race setup) saw this and said he has a rolling problem with his at around 1700rpm, the speed rolls up and down significantly on its own. He is going to add a little tension to the spring and see if that helps. I will post some feedback when I hear anything.

[divace73]

A friend of mine with an X1/9 (race setup) saw this and said he has a rolling problem with his at around 1700rpm, the speed rolls up and down significantly on its own. He is going to add a little tension to the spring and see if that helps. I will post some feedback when I hear anything.

Also get him to check the track mark wear on the PCB board, it can be adjusted slightly so the AFM can run a new track.

[RRoller123]

Yep I did that too, ~1/16" lower, and recommended it to him.