Unkle

Had a very slight hesitation on random throttle application (it happens rarely but bothers me even though its so slight i thought i was imagining it). Also hunting on start up on very cold days. So checked distributor caps, rotor arms, coils (even though they are new Bosch items and less than a 2000 miles old), misted the leads at night to check for sparks, New Bosch Lambda, swapped the DME Relay. Nothing was wrong.

So I took the Air flow sensor unit off and cracked open the cap. Cleaned the chamber and used electrical contact cleaner with cotton buds and cleaned the sensor tracks that sweep in an arc to make sure it was getting a clear signal. I read somewhere its only 4v at WOT so its a sensitive part that can cause DME relay type trouble or the above that i checked and pretty much a load of other things so I assume its fairly delicate. Popped the cap back on and used Loctite clear sealant thats circuit board safe to reseal.

Cleaned the WOT and Idle micro switches with contact cleaner too.

It was 2*c today so with the car lying up for a week I started the car and it started without hunting and drove very smoothly, in fact it was the best its been in 18 months since purchase. I have fitted lots of parts and none of then seemed to change the feel until now, so if anyone has the same issues and has checked the things i have, as has been mentioned before on RL, the AFS could help with a little free cleaning

ray stobbs

nice clear photos thanks might have a go at that looks very delicate

Goughary

Can you shoot some pics from farther out? Which part is that and where is it?

FeralComprehension

It's the airflow meter; just past the filter/airbox on top the motor.

Unkle

Your right I didn't fiddle too much, i just pushed the flap open to move the brass looking contacts along so i could clean the area completely. The hardest part was getting the black cap off without breaking it, but its fairly robust, you can see some of the clear sealer used originally on the top edges of the unit, but i stanley blade and a screwdriver in a few places broke the seal.


^^ It is. When you push the flap (barn door) in the air flow sensor the 3 brass contacts slide along the arc on the circuit board, and i assume give a signal to the DME. The Arc on the circuit board can be pitted/damaged or just dirty from what i have read. Luckily mine looks in good condition, however the cottom buds still looked black after some cleaning.

RicardoD

Great thread. So many good posts recently to file away for future reference.

Goughary

Thanks. Didn't even think to open that up hen I was cleaning my intake a few weeks back. I still haven't reinstalled, so I'll be opening it up this week to check it out...good stuff.

Babalouie

I wonder if it might be a good idea to put some sort of lube on that sliding electrical contact? (it looks so delicate)

Unkle

I saved a link from ages ago about the AFS, I decided not to follow the article and refurbish as it suggests, mainly because i didn't think i had a major issue. But i guess its doable, Applying lube? I wonder if its ok to do it, i left it dry as it looked like Bosch left it dry from the factory, (no obvious lube visible)

http://www.the944.com/afm.htm

I noticed in the article (link) it has only 2 tracks for the sweep on the 944, where as the 964 has 3, perhaps a revision? Or the 964 system requires more info for other things? Either way i was not convinced of the need to undo and move things about even though mine has sweep marks, I kind of thought - wont they all have marks after a short period of driving? I guess its just important to not have pitting in the sweep area and if that's fine then the clean up and refit should be all that's needed.

stevepaa

Just did this. My car was bouncing idle all of a sudden. It has stalled recently. The code was 21 air flow sensor. So I cleaned the tracks and moved the arm a touch to get new tracks.
Did adaptation with scantool and idle sits at 750 in drive. Was dipping below 600 and stalling before.

Thank you ricardo and tom.

Beachie

Hi Unkle,

I've been looking at various threads as I've just pulled my '89 964 C4 (92k miles) out of hibernation and had my first mechanical issue with it, and I'm wondering if yours would apply to me;
First drive after hibernation, started first turn of the key as usual, usual hunting of engine for a few seconds after cold start, nothing unusual. drove it around town for about an hour, ran nicely. Put my foot down for the first time that day and the engine cut out like it had been switched off. coasted to a stop, poked around a bit with no tools, checked fuses etc. after about an hour it started and I drove slowly home, fine. Yards from home I put my foot down again to see if problem would repeat, and it did.
Checked forums, bought new DME relay and fitted. Drove the car slowly but after 10 mins it cut out and died again, this time pulling away slowly from traffic lights. switched DME relays back over to see if it was related to heat in DME relay but wouldn't start.
I'm due to get the car serviced shortly but I would like to know if I can sort this without massive expense from the dealer first, especially as it will involve having the car relayed to the dealer which will only add to the expense.
Do you or anyone else have any ideas?

Thanks

dlg993

Thanks, Unkle. Now Sep 2016, and your post continues to be relevant. With regard to lubricating the resistance-wire tracks, obviously a non-conducting lubricant might be used, but it also shouldn't be applied in sufficient quantity to be insulating. I will likely use Aerokroil in cleaning my unit; it dissolves corrosion and provides a mild lubrication.

dlg993

Hello again Unkle. My vehicle is an '86 Carrera. I removed the air flow sensor, and cut the perimeter seal on the cap. But, I was unwilling to use enough force to remove the cap. I tried a wooden block and soft hammer, but with no success. You mentioned using a screwdriver. Did you use it as a pry-bar, or hitting lightly as a chisel? I'd prefer not breaking the cap.