Another 1987 Carrera bucking/stuttering AFS problem with a (I believe) unique issue

[Tippy]

So, after thinking my idle microswitch was bad and replacing (I did the continuity test and thought it was bad), my stumbling, stuttering, and backfiring Carrera still stumbles, stutters, and backfires. Back to the beginning I thought.......

I tested all the sensors and they all checked good at the DME harness.

The one sensor I hadn't tested was the AFM since at the time I did not have a 9-volt battery harness to hook to the AFM pins - but I got that made today.

When I tested the AFM, low and behold, the first so-many-degrees did not raise the voltage reading on the multimeter. It started at 0.445V and held there until approximately 10 degrees give or take and then it would hit like 0.485V and smoothly and incrementally go higher.

Score!!!!!

But wait, the track in mine is very light, nothing like the ones I have seen online.

Hmmm......

Whenever I would eyeball the voltage raise as I turned the wiper, I noticed the voltage would not change until it got out of the 1st section (the first section that is connected to the first strip leading away from the track area).

Does this mean the potentiometer board is dead on the closed throttle side because the first section circuit is bad? Is there no repair?

Hope I made sense....

TIA, Cory

[Joe Bob]

You can try cleaning it.....I've been told and eraser works. At least it did when I used it on my 914 with a similar issue.

[DRACO A5OG]

It is now time to take apart the AFM and look at the potentiometer strip, post a pic.

If you do reposition the arm be very careful the tension is close to OEM as possible. Take not of the tension prior to adjustment.

+1 on a clean eraser, just be gentle about it.

[Tippy]

(Grainy iPhone pic)

Here it is:

[Tippy]

Referring to pic above; see where the farthest right strip contacts the track area in the idle area (where the wiper is pointing)?

That is where it is dead.

Past that point where the strip contacts the wiper track, the voltage gains nicely.

The wear is very minimal all throughout the track making me think the first circuit is dead and I have already cleaned the track without fixing the issue.

[DRACO A5OG]

As I recall, the screw can be loosened to allow the arm to be ever so slightly adjusted, but doing this will advance the entire range,

It might be ok if you adjust to the left and the reading is the same, but maybe. Get a reading through out the range, adjust and see how much of a change it takes on.

[Tippy]

Ooh, I don't want to play with screw!

Anyways, I had my wife push down on the wiper with a pencil eraser and the voltage would not increase while opening.

The first circuit must be dead.

Can these boards be bought by themselves???