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s0rr0w · Post by **s0rr0w** » Sun Dec 03, 2006 5:46 am

Hi guys..
I started the car yesterday"all fine", But when i tried to get the revs up a bit, it just didnt want to go, heard a knock, knock noise coming from the front..
Stuck my head in the bonnet, and found that the knock noise came from the AFM.The big flap that lets the air in, its like it tries to open, and then gets forced closed again ?

Is my AFM stuffed ? any way to fix this ?

Thanx..

jol · Post by **jol** » Sun Dec 03, 2006 6:24 am

s0rr0w wrote:Hi guys..
I started the car yesterday"all fine", But when i tried to get the revs up a bit, it just didnt want to go, heard a knock, knock noise coming from the front..
Stuck my head in the bonnet, and found that the knock noise came from the AFM.The big flap that lets the air in, its like it tries to open, and then gets forced closed again ?

Is my AFM stuffed ? any way to fix this ?

Thanx..

I think It's just not opening/closing smoothly, or the rubber stop at fully closed might be gone. Remove the rubber hose and feel if its sticking at some point.

If it proves to need replacement and you can't find any from alfas, you can do as I did and pick a late 80/early 90 bmw meter and replace all electronics/guts. Two of the connectors screws dont line up but I'm sure your'e handy with a drill

Also it probably need recalibration afterwards.

Murray · Post by **Murray** » Sun Dec 03, 2006 6:48 am

Have you been messing with the AFM spring ? Sounds like the spring has lost its tension.It's easy to check just remove the air filter and use your finger to see if the flapper has spring tension when you push on it.If it doesn't your about to take a major lesson on AFM calibration.

jol · Post by **jol** » Sun Dec 03, 2006 6:52 am

Murray wrote:Have you been messing with the AFM spring ? Sounds like the spring has lost its tension.It's easy to check just remove the air filter and use your finger to see if the flapper has spring tension when you push on it.If it doesn't your about to take a major lesson on AFM calibration.

Why? Tension it until it starts and run somewhat ok, finetune using a wideband o2 meter (rent from a speedshop perhaps).

s0rr0w · Post by **s0rr0w** » Sun Dec 03, 2006 11:28 pm

Thanx for the reply's

Nope, i have not been fidling with the afm.

What could cause the spring to loose tension

I'll go have a look tonight, will let you know.

Thank You..

Murray · Post by **Murray** » Mon Dec 04, 2006 1:48 am

Nope, i have not been fidling with the afm.
What could cause the spring to loose tension

sOrrOw they don't "normally" loose their tension unless they have been inproperly adjusted.There's a screw that sets the spring's tension under the black plastic cover.That's why I asked if you'd been in there. Check the flapper door and let us know if that appears to be the problem.

s0rr0w · Post by **s0rr0w** » Tue Dec 05, 2006 12:24 am

Hi
I had a look at the flap "it has spring tension on it"
Any ideas

Anything els i can look at ?
Here r some pics, if it'll help.
Thanx..

Murray · Post by **Murray** » Tue Dec 05, 2006 2:02 am

Your AFM spring assembly looks normal.Two things I do notice:

1) Time for some housecleaning.The inside the AFM should be sprayed with some carb cleaner.It's important that all the grunge be removed to ensure smooth movement of the "flapper".

2) May just be the photo but in the last one the edge of the "flapper" looks crooked .Have you had a backfire recently ? If it is crooked that will prevent proper full movement.

Sporttunergtv6 · Post by **Sporttunergtv6** » Tue Dec 05, 2006 7:12 am

could it be a low fuel pressure? one time i had a kinked fuel hose back by the fuel pump and when i got on the gas the motor would almost stall and the afm flap would slam shut as motor stopped sucking air.
v

s0rr0w · Post by **s0rr0w** » Wed Dec 06, 2006 1:39 am

I'll clean the afm properly tonight, and try to take some better pics..

I did in fact have a backfire over the weekend "while i was trying to get some revs" do you think it caused any damage ?
What caused the backfire ? too much feul, not enough air ?
Can i just try to bend the flap straight'ish ?

Thanx for that tip Sporttunergtv6, i'll have a look at the pipes tonight.

Thanx for the help guys..

Murray · Post by **Murray** » Wed Dec 06, 2006 2:00 am

sOrrOw a "backfire" up through the intake is most commonly caused by using the throttle on startup.A well tuned engine should not require you to touch the accelerator pedal on startup - particularly cold.First thing to check is the ignition system particularly the rotor and cap.Ignition timing must also be close to spec.If you don't have solid ignition, fuel will build up during cranking and... boom.
You may as well attempt to straighten out the flapper but you have to get it such that there is absolutely no binding through its full range of movement.If that is not possible you can find a replacement AFM fairly easily and they're not too expensive. Given the explosive forces involved odds are pretty good that you've dislodged the rubber connectors between the plenum and the intake tubes so you better give those a close look as well.

s0rr0w · Post by **s0rr0w** » Wed Dec 06, 2006 11:32 pm

I dont need to use the pedal to start the car.Just a crank, and it starts..The backfire i got over the weekend, was while i was onening and closing the throttle with my hand, while looking if i could see something in the afm.Here's some clean pics. Ill try and find a replacement afm..

Thanx for all your help..

Murray · Post by **Murray** » Thu Dec 07, 2006 3:10 am

s0rr0w it looks good now.Before replacing it, have you tried opening the flap to see if it binds at any point of its travel ? It may still be usable.

Barry · Post by **Barry** » Sat Dec 09, 2006 5:37 am

Does your car start and idle?
If so,is it firing on all cylinders?

s0rr0w · Post by **s0rr0w** » Sun Dec 10, 2006 2:59 am

The flap has smooth movement, all the way from closed to open.
Cleaned the whole thing, all the tracks and contacts inside the afm aswell..
The flap noise seems to be almost gone now.

The car usually started first time, just by turning the key..
Only started on the fifth turn this morning, lots of smoke out the tail pipe.
I also noticed some petrol coming out the little rubber pipes that sit above the injectors.

I changd the petrol filter a while back, do you guys think that it could be a dud ?

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