AFM flap must have bent, L-Jet tweeked for a 1911 cc Options

[malcolm2]

I decided to drive the 914 this morning. Not sure if the weather had anything to do with this, but it is about 25 *F. Car is in the garage, so I might be a bit warmer.

I have put about 25K miles on the completely re-built car in 3 years with very few issues. But this morning I heard a muffled back-fire at start-up. But the car started. It idled a bit high, but I let it warm up.

The car died in the street as I shifted to 1st. I could hear the fuel pump running after the car died. It restarted fine, but would not rev. I finally got it to respond to the throttle and I put it back in the garage.

Since the fuel pump was running I was afraid the AFM was stuck. And it was. It now takes a good bit of force to push open the AFM flap and I hear a BIG squeak. Like the flap is rubbing on the box. The AFM flap stops moving when I stop pushing and have to push it back from the other direction.

Can this be repaired?

Clark

[jim_hoyland]

Have you opened the plastic top cover and check out the mechanism ?
Brings back memories: had this happen when I took my first road trip in the 914. Ended up having to replace it

[malcolm2]

Have you opened the plastic top cover and check out the mechanism ?
Brings back memories: had this happen when I took my first road trip in the 914. Ended up having to replace it

yes, I took the cover off too. seems to be fine. I thought maybe the spring was the problem. But it was operating as I forced the flap.

[jim_hoyland]

I can't verify this but once heard the flap is subject to damage if a backfire occurs ??? Hence some P cars had relief valves in case ?!

[porschetub]

The flap can't bend,remove the afm and give it a clean with throttle body cleaner,do remove the cover (as mentioned ) and check the action of the spindle,give the contact board a clean @ the same time.
I had one go like this on my old E28 2.7 ,worked fine after the above procedure,they do can get a bit s#ity inside.
Good luck.

[malcolm2]

"The 1.8 air flow meter often fails when a cold engine lean backfires, warping the sensor flap. This warped flap sticks in the bore causing a rich mixture and an idle that goes away as the engine warms. Replacement is the only solution, however it is important to cure the lean running engine that initially caused the problem, change the gas flooded oil and never again depress the accelerator pedal when starting a cold engine."

The above paragraph is from AutoAtlanta, part # B473906301. I am not positive, but I could have been pressing the accelerator.

[jtprettyman]

You are welcome to try mine if you think it will help troubleshooting. It is in the same untested shape as my TB was.

[southernmost914]

I had this happen twice on a 1.8L years ago. Bottom of the AFM warped when the car backfired on start up. The first time I had the dealer replace it$$$$. The second time I bent it back and drove from Ohio to Key West with never a problem again. I do believe I stepped on the throttle before starting it when cold.

[malcolm2]

I had this happen twice on a 1.8L years ago. Bottom of the AFM warped when the car backfired on start up. The first time I had the dealer replace it$$$$. The second time I bent it back and drove from Ohio to Key West with never a problem again. I do believe I stepped on the throttle before starting it when cold.

That is the kinda story I like to hear. DIY and save $300. And it makes some sense. Looking at the flap this morning, it did not look bent. I guess I had mis-read or mis-heard about the flap being damaged.

I'll take a closer look at the box. I bet the squeaking is the flap rubbing on the warped box.

Thanks.

[jim_hoyland]

Yup; never depress the accelerator at start up. Tell us if this is fixable. I keep a spare AFM and dual relay -just in case

[malcolm2]

I think this is just a generic picture. But if I shine a light thru in the direction of the air flow, I never see the flap labeled "measuring plate" touch the top, bottom or side of the box.

So I have to assume that the "compensating plate" or maybe the yellow "circle thing" in the middle is what is touching.

Problem here is I just don't know what needs to be RE-BENT. I can't really get to anything but the measuring plate and the part of the box the air goes thru around the measuring plate.

This thing does not look like it comes apart at all?????

Any ideas?

[jim_hoyland]

There must be a way to open it and R/R parts; there is a least one company that rebuilds AFMs
Try a search with +flap +repair; or some combination of key words

[malcolm2]

There must be a way to open it and R/R parts; there is a least one company that rebuilds AFMs
Try a search with +flap +repair; or some combination of key words

Even the generic drawing i found looks like it has rivets on it. My bottom plate has lots of small dots that are probably rivets or pins that they smushed. The whole btm plate has a silicone sealer on the edge. So it was 2 parts at one point.

[southernmost914]

My base/floor seemed to be all epoxied in. I simply marked were it was rubbing and used a wooden dowel and a mallet to slightly work it out through the air way. It did not take much pressure to level it out. The floor/base of the unit is what had warped.

[Rand]

Bent? How would that happen? Ok, back to your normally scheduled programming...

[malcolm2]

I figured I would add a squeaky video. As I remember the flap in the AFM is supposed to return to the closed position and not SQUEAK.


https://www.youtube.com/watch?v=e3KIRf2ZXf0

[southernmost914]

I figured I would add a squeaky video. As I remember the flap in the AFM is supposed to return to the closed position and not SQUEAK.


https://www.youtube.com/watch?v=e3KIRf2ZXf0

Looks like it is rubbing in the chamber.

[Valy]

That is not good but you know what ypu need to replace now.
I never tried this but the junkyards are full of other cars with LJET and the same AFM, but each one has a different resistors board. Maybe you can just replace the mechanics or just the flap if you don't find a 914 one.

[michael7810]

There's a NOS AFM on craigslist Phoenix, part number 0 280 200 006. The ad says it fits a 914; no price is listed. Search on Porsche 914 and it comes up if you are interested. It's not far from me and I'm willing to help out with shipping if the seller only wants to sell local. Good luck

[ClayPerrine]

I have been working on an L-Jet 914 for over 30 years. Yes, the flap can bend from a backfire. It will cause all sorts of bad running issues. Best solution is to replace the AFM.

The later model AFMs have a "backfire valve" in the flap. It is a spring loaded valve that pops open if the engine backfires, preventing the warpage of the flap.

And don't step on the accelerator when starting.