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Hi all

It would appear that the Air Flow Meter on my 164 qv has a dead spot that kicks in at 2500rpm, creating the mother of all stutters and misfires :shock:

feel free to suggest other alternative faults?

Ive split the top case to inspect it and attempt a refurbishment but i think i'm pee'ing in the wind to be honest, so has anyone got one of the old mechanical flap type AFM hanging around?

Maybe even to try first of all to make sure its that AFM giving me this symptom but i'm pretty sure.

The bosch number is 0 280 203 026 and is shared with a couple of fiats and the porsche 944 i believe.


Thanks in advance
 

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Not much you can do other than buying an ebay unit for 300 squids or a new bosch part for 600.... Are you sure it is the AFM? Flat spots can typically be caused by dirty connections on the amplifiers.
 

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I've shifted the ceramic substrate on one of those before to give the wipers a new bit of track to run on but you end up having to mess with the thing a bit to get it back to where it needs to be. Loosen the screws holding the substrate down, shift the whole thing towards or away from the pivot point - whichever gives the cleanest track for the wiper, nip up the screws then start messing! I found I had to fiddle with the spring tension a wee bit using the big black (IIRC) plastic adjuster ring, as well as idle mixture. A small movement makes a big difference so creep up on it if you go down this route.

Might be worth seeing if it is indeed faulty though - ignition on, engine not running, measure the output voltage and move the flap slowly and carefully from closed to fully open while watching the volts. Any sudden dips or changes and a worn track is likely. If it's smooth, fault is likely elsewhere. I don't believe it's a linear relationship between deflection and volts, but it should be smooth IYSWIM.

Crank trigger maybe more likely than AFM perhaps? If it is always rev related and not load related, then it almost certainly isn't the AFM.

Iffy sparks is another good shout as well from V6J
 
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