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Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure
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blackglasspirate
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PostPosted: Tue Oct 11, 2016 8:53 am    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

So, I'm trying this procedure again while on the road because of a bad idle but am running into an issue. Whenever I unplug the ICV the engine dies immediately. If I unplug it before starting the engine, it won't start at all.

Any ideas why that would happen?

With it still connected I am getting around .5-.6v, but I'm guessing that's a somewhat false reading if the ICV is still connected.

Thanks!
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jberger
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PostPosted: Thu Oct 13, 2016 9:44 am    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

blackglasspirate wrote:
So, I'm trying this procedure again while on the road because of a bad idle but am running into an issue. Whenever I unplug the ICV the engine dies immediately. If I unplug it before starting the engine, it won't start at all.

Any ideas why that would happen?

With it still connected I am getting around .5-.6v, but I'm guessing that's a somewhat false reading if the ICV is still connected.

Thanks!


Did you set the ICV with an amp meter? This step is very important. You don't need a special tool, just one wire from male to female connector and the other goes through your amp meter.

With your O2 connected .5-.6V is ok.. Sometimes they will be quite steady. The ICV doesn't have a lot of effect on that. Some but not a lot. Unplug your O2 and check.
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rocinante dapple
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PostPosted: Sat Nov 05, 2016 4:48 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

Can this procedure be adapted to an air cooled (1980) vanagon? As far as I understand I don't have an 02 sensor to read the voltage from when adjusting the meter.

My AFM is causing a rough idle, but stabilizes, with varying hesitation from idle, when the throttle is engaged. The thing I noticed when I pulled off my plastic cap was at idle, the meter is jumping all over the place, but with the throttle engaged it is more or less stable. And, just out of curiosity, I briefly manually held the arm in place to keep the air meter stable and it improves the stability, go figure, of the idle dramatically.

I have cleaned my points, although I haven't checked my continuity between all the points in the system though. I have a new temp 2 sensor, I have replaced the double relay for the fuel pump, but eventually found that the original one did better after I cleaned it up.
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pathao
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PostPosted: Sat Nov 05, 2016 6:29 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

rocinante dapple wrote:
Can this procedure be adapted to an air cooled (1980) vanagon? .


You may want to check this out

http://www.itinerant-air-cooled.com/viewtopic.php?f=50&t=7761
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jerryherb
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PostPosted: Wed Feb 22, 2017 11:53 am    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

brutisbus wrote:
Thanks, .95 V means too rich, so I thought if I had a leak it would read lower V -lean, but with all the feed back loops in the system, who knows. It does stall out if I turn down the mix screw, so the engine is responding just not showing up in V readings. I just wish I had a baseline I could set this AFM to to start from. How many turns out on mix screw, appx where wiper should be at engine off, and were at idle, what's the normal turns out in idle speed plug. The whole thing is such a cats cradle it would be nice to know where to start from with a system that has been tinkered with buy someone else I'm not confident with. Ugh, and I'm supposed to be heading out on a 3K vacation road trip in a week and tomorrow is one of the last days available to work on it, Murphy is at it again!


Yes, a base line setting would be nice. the only base line i found for AFMs relates to AC FI systems. 60g weight is to crack the flap slightly - spring base line (see second link), but not sure it applies to digijet/digifant AFM's. it should also be noted that 1.1-1.2V is the AFM voltage at idle as that is where they all wear out (see van-cafe shoebox manual for optimal AFC voltages at idle and speed). setting this on my AFM (previously tampered with) gives it a nice idle when warm though running rich (.9V+). When warm it also needs a gas pedal boost to bring it from low idle to proper 950 and runs steady from there. on cold start runs low idle and stumbles until warm. all done in open loop mode, O2 disconnected. When plugged in and warm the rough idle comes back as ECU is trying to lean it out, and sometimes POPs at WOT (probably preignition, though timing is set at 35-40 all in). if anyone else has the base settings for digijet/digifant it would be swell. I still have to test clean the Aux Air Regulator to see if crappy cold idle is due to lack of extra air at warm up. my latest testing and adjustments of the AFM are based on these:

way better calibration technique (AC AFC)
http://www.itinerant-air-cooled.com/viewtopic.php?f=50&t=7761

60g weight flap/spring adjustment:
http://www.thesamba.com/vw/forum/viewtopic.php?t=524738&postdays=0&postorder=asc&start=0

shoebox with 1.9 adapter manual (im experimenting with a 1.9 late 85, which was parked under a tree for a good while):
http://www.van-cafe.com/shop/images/8385-user-manual-troubleshooting-guide-9-26-08.pdf

at this point i need to get a wideband gauge (MTX-L) to investigate further, replace the cat with a straight pipe to prevent clogging while trying to resolve the rich running issue, and fix a slight exhaust leak at cyl 4 (damn dansk aftermarket header's exhaust hanger screw head is in the way). leaving the O2 disconnected for now.

so far replaced all sensors and tested at the ECU plug as prescribed. adjusted timing (was waaay advanced). could not locate a single vac leak with propane, but have not connected a vac gauge as of yet.


Last edited by jerryherb on Wed Feb 22, 2017 1:20 pm; edited 2 times in total
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jerryherb
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PostPosted: Wed Feb 22, 2017 1:03 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

can someone actually provide some base settings from an unadulterated AFM (force/weight to open a flap, voltage at idle, # of turns of the CO screw, etc)? there is not need to open the AFM for this. variables from a NOS would be nice, but i guess refurbs "should" be up to factory spec, whatever that means, and not based on individual engine's behavior. my original AFM has a 013 mark on the spring so that is what i would be most interested in seeing (late 85 1.9 digijet system).
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