Volkswagen: VW Air Flow Meter, air flow sensor, air flow meter

Question
Hi Ron,

I am the owner of a convertible 1976 Fuel Injected Super Beetle. It's a Californian import, I now live in Canada.
Over the last 3 months I've had engine issues (backfiring and the feeling of running on 2 or 3 cyclinders only). I've replaced plugs, plug leads, dist cap, rotor, points, condensor, ignition coil, fuel pump, fuel filter. It has now been to three garages and a retired VW mechanic, and still the problems persists.
Today with the VW mechanic we discovered with an ohmeter that the resistance across the terminals of the air flow sensor did not lessen or increase linearly, but was quite eratic when the flapper was pushed. The Bug used to run ok when the throttle is kept at a steady position, but then misfires badly under acceleration or decelaration. IT is also not consistent, and will sometimes run just fine. Without cutting the plastic cover to the meter off through the flexible/silcon caulking (which I'm scared to do in case it shatters or I can't get a replacement), is it possible to tell the condition of the potentiomter.

I'm assuming that the problem is in no way connected with a starter that randomly doesn't throw in, though the fuel pump runs on turning of the key. Often a few minutes delay here will see it start fine.

Thanks in advance

Martin

Answer
Martin,
 First of all, you've done quite a bit of good troubleshooting.  There are only a few more components left.  Now as far as the air intake sensor, the Bentley manual says:

At the six pin connector(1976 models only):
- Pin 6 to 9 = 100 to 300 ohms
- Pin 8 to 7 = 80 to 200 ohms

There is no expectation of a "linear" change.
The pins are number strangely. When looking straight at it from behind the car, they are numbered from LEFT to RIGHT as follows:
39, 36, 6, 9, 8, 7

Also, you should make sure the flap is moving smoothly.  Disassembly of the airbox is recognized as part of the maintenance process, so don't be afraid to unscrew and pry it open.  You do need to re-seal it with silicone when finished.
There are a couple other possible problems, most of these making the air/fuel ration too rich:
- Bad temp sensor I in the airbox.
- Bad temp sensor II on the drivers side engine head.
- The Auxiliary Air regulator is stuck open.
- The Cold start injector is stuck open or leaking.
- The Thermo-time switch is bad, keeping the cold start injector on.
- A vacuum leak somewhere in the system.
- Bad fuel pressure regulator.

Rick