AFM Maintenance

[TINGY]

Since i've had my turbo i have had recurring issues with the AFM. The car would start running sporadically and the rpm's would shoot up while you were idling at the lights, while sitting on a speed and backing off the throttle the car would keep surging along with no input from the throttle, also the car would just lose power and when you would input the throttle it would fart and sputter and you would have to pull over and when i stopped the car would stall, it would turn over and start but would not keep running.

I would then have to turn off the ignition and pull the plug to the AFM then go and turn the ignition on and then re-plug the AFM, somehow this re-sets the AFM, only then would the car turn over.

I would then get going again and for sometimes 4 weeks or 4hrs all would be ok and then it might happen again. The last 2 weeks it has been playing up and it stopped on me Friday, prior to this the car was surging when i backed off and would sometimes rev for no reason when stopped.

After a bit more research and finding a youtube video i decided i would tackle re-setting the pickup in the unit by moving the copper wiper on the actuator.

What happens over time is the copper wiper wears into the resistor strip causing tracks to form, so i moved the wiper just like the video and today tested the car on a 2 1/2 hr drive with no problem what so ever.

I'm hoping this is a fix until it starts to wear another groove into the strip.

This is a fairly easy job that anyone could tackle, getting the cover off requires lots of patience though and a careful hand pulling apart the rest if it, one slip would significantly damage the unit.

The video does not show every aspect of the job but there is enough info to work out the rest of it, in the turbo it's possible to do it in the car.

This first picture you can see where the wiper has been wearing into the resistor strip, my bodgy yellow arrows point to this, the green arrows show where the wiper will run now, this is off my car.

This picture shows the wiper you need to adjust

   

[tazzieman]

Yes I did that way back due to a flat spot on acceleration. I would also caution against heavy hands as it's possible to bugger this up! It's a pretty delicate mechanism.

[TINGY]

Tazzie have you had any problems at all after this fix, how long ago did you do yours.

[Rob]

Stephen, "while you're in there", make sure the "barn door" isn't binding on the bottom of the AFM body.  Mine was, due to a build-up of material that only caused binding when hot.  Let it cool down and all seemed good - until next time.  A bit of time with some 400 grade wet&dry fixed the problem, almost 3 years ago now...

[cyberpunky]

While it provided nearly 30 years of reliable service, in my case, the reality is even Porsche went to better methods a few years later. The fact they are NLA means you can end up chasing your tail with them and even sourcing another means you are going to pay top dollar for a part that may fail shortly after fitting it. Once mine started giving me grief it was never the same. After seeing the tracks I was surprised I hadn't had more problems earlier.

[tazzieman]

Tazzie have you had any problems at all after this fix, how long ago did you do yours.

None at all. Revs smoothly up to redline. Did it in 2012.

The only other issue I had was a bad idle which I eventually traced to the funny J shaped vac hose under the manifold - a hairline split. Not sure if the turbo version has this.

[Plugger2]

Since there are quite a few MAF conversion kits available for the Turbos, of I were a Turbo owner I'd consider retiring the AFM but keeping it for "originality" purposes down the track, and go with a MAF in the meantime. Most if not all conversions are completely reversible, of course. The only consideration might the $$$, but if the MAF was already showing signs, it might be more economical long-term than running the MAF into the ground. Just a thought.