Afm Identifiation And Component Question

[mhyphenl 10 1 Cars]

Firstly is the following AFM part number correct for the model.

 

XU9JAZ DKZ, AFM: 0280202202

 

And can anyone tell me how the component where the idle mixture screw should be actually works. As far as I'm aware the older idle mix screw just lets a bit of un-metered air through. This looks like it should adjust the voltage read accross the afm pins to effect the same adjustment. The only thing is, I've measured the voltage accross the pins for the afm and turning the screw on the blue thingy does nothing at all!?

 

[welshpug 1,663]

Motronic ecu's dont use an air bleed, its a potentiometer, looks like there are a few bits missing.

 

I think its exactly the same pot used by the MAP sensor based MP3.1 as well, in which I replaced the pot itself with one from maplin as I couldn't get the emissions down, problem solved for a few quid.

 

 

From what I recall you need to apply a voltage not just measure the resistance, there is/was an article online by a 944 owner, its very much the same unit used on them.

[mhyphenl 10 1 Cars]

From what I recall you need to apply a voltage not just measure the resistance, there is/was an article online by a 944 owner, its very much the same unit used on them.

 

Hi Mate,

 

thought so. I read the voltage accross the terminals with the car running so the voltage was being supplied in 'real time' as it were. The track is working fine, no voltage drops and while running it was nice and smooth. I was expecting to see the voltage at idle change slightly by changing the pot but it didn't. kinda made me think that component was faulty.

 

Any idea what might be missing??

Edited April 12, 2016 by mhyphenl

[welshpug 1,663]

I've never seen the insides of a motronic afm I'm afraid.

 

But even then, if you turned the screw on the pot directly and nothing happened I would replace the pot.

[mhyphenl 10 1 Cars]

good point well made I'll try that first before splashing out on a new one.

 

By the way, this is listed as part number 0280202202 for Alfa / Vauxhall. with Peugeot part no 1920 93 which is what service box confirms for a DKZ car:

 

http://www.ebay.co.uk/itm/131758147834?ssPageName=STRK%3AMEBIDX%3AIT&fromMakeTrack=true

 

It's not a Bosch Original but neither is mine. This should be fine if I decide to replace shouldn't it?

[Ryan 99]

The Motronic AFMs send a separate signal back to the ECU for the position of the adjustment pot. Then the ECU software does any alteration needed. One of the other AFM pins will have a voltage that changes when you adjust the pot.

[mhyphenl 10 1 Cars]

The Motronic AFMs send a separate signal back to the ECU for the position of the adjustment pot. Then the ECU software does any alteration needed. One of the other AFM pins will have a voltage that changes when you adjust the pot.

 

Now that's interesting. Any idea which pin? There are only 4 connected pins. One is the 5v supply, one is the earth, one is the flap signal and one is the temp sensor. Maybe they piggyback the adjustment to the temperature signal then. That would alter the mass calculation and thus how much fuel to add!?

[Ryan 99]

Apparently on catalyst models the adjustment pot isn't used, so the loom doesn't have the wire for it.

[mhyphenl 10 1 Cars]

Oh, ok that probably makes more sense, the lambda does it exclusively then! I think the main issue is an air leak then! Or lazy lambda! I'm going to have to have a thorough look for air leaks!

[petert 592]

Part wiring diagram from a XU9J4Z M1.3. It's mostly identical to DKZ. M313 is the AFM.

[mhyphenl 10 1 Cars]

Hi guys,

 

just had a very detailed look at this, the trim resistor which is the blue thing, in itself does work. it's a 1k variable resistor and I can measure the resistance varying at either end between pretty much zero and 1k. However it doesn't appear to be connected to anything. The simple circuit is molded into the black plastic cover so it's hard to really see what goes where but using a continuity meter it seems as though it's not connected. If you look closely there are holes drilled through the black plastic right through some of the circuit tracks. I think they make that black cover the same then drill through bits depending on what model the unit is for.

 

Ryan, it looks like you're right! on Lambda models the trim isn't used as the lambda should be doing the adjustment.

 

The only thing that threw me a little is that a guy on FB swears blind that all models should have a trim pot in motronic 1.3. Basically called me an idiot for thinking otherwise!?

[welshpug 1,663]

certainly sounds plausible, i can't see any reason you would still use the pot if it has a lambda.

 

there are variants of the later MP3.1 that use either a pot in some vehicles (zx, bx, 405) and a lambda in others (106)

[mhyphenl 10 1 Cars]

certainly sounds plausible, i can't see any reason you would still use the pot if it has a lambda.

 

there are variants of the later MP3.1 that use either a pot in some vehicles (zx, bx, 405) and a lambda in others (106)

 

Yes, the holes drilled are too neat and deliberate to be anything other than to disable the trim pot for models with lambda. It's such a cheap component, a couple of pence in bulk that it's probably cheaper to make all the black plastic housings the same and then disable the pot with some holes that manufacturing two different housings!

 

On that basis I have a fairly major air leak that I cant find as the engine is running lean and the lambda isn't able to adjust it enough. Spark plugs have a slight grey residue which suggests lean and the revs rising and the light coming on is the Lambda trying to adjust the mixture richer but failing to do it enough and going 'out of range' i guess.