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Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure
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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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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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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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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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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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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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brutisbus
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PostPosted: Sun Sep 11, 2016 7:11 am    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

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!
AZ Landshaper wrote:
sounds like your adjustment screw isnt doing anything if the V doesnt change when you adjust the screw. When I have this type of issue I start looking for vac leaks. Thats the type of thing that negates the adjustment screw, already having lot of air leaking into the system. Have you ever run a smoke test on the motor? A cheap way to sleuth out vac leaks is to add pressure to the system w a bicycle pump and spray the joints and hoses with soapy water while looking for bubbles. My 1st attempt at doing this revealed a lot of leakage. But beware! keep the pressure to below 5 psi or you could create new leaks by blowing out a seal.
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AZ Landshaper
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PostPosted: Sun Sep 11, 2016 6:22 am    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

sounds like your adjustment screw isnt doing anything if the V doesnt change when you adjust the screw. When I have this type of issue I start looking for vac leaks. Thats the type of thing that negates the adjustment screw, already having lot of air leaking into the system. Have you ever run a smoke test on the motor? A cheap way to sleuth out vac leaks is to add pressure to the system w a bicycle pump and spray the joints and hoses with soapy water while looking for bubbles. My 1st attempt at doing this revealed a lot of leakage. But beware! keep the pressure to below 5 psi or you could create new leaks by blowing out a seal.
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brutisbus
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PostPosted: Sat Sep 10, 2016 8:21 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

A local mechanic working on my engine pried open my AFM to deal with a misfire issue, ended up being plugs! I could of fixed that, but since it was there for other things I said check it out. I was disappointed when I got it back and I saw that a newly installed re-build AFM I put in 6 months ago had a mangled cover and the Idle mixture screw cover was missing as well. Anyway, I was digging into some 1K-3K RPM hesitation when I decided to replace my O2 sensor. Suddenly I have a bunch of power at low end but now it stalls and smells very sulfur like. Anyway, I followed this AFM adjustment procedure (thanks!) was excited I could do this without a CO sniffer. The previous mechanic had the Mixture screw out 7 turns, I started adjusting there but no matter how far out I came the V reads .9-.98. So I reluctantly took off the freshly sealed AFM cover and adjusted the wiper, slightly, still no drop, then the spring, still no drop in voltage. (did negatively effect run-ability though) On a side note, I heard a rattle in the exhaust at idle and still trying to figure that out but it sounds like maybe the cat might be loose/broken, that would suck cause it's new with only 17K on it and the new GoWesy SS system. Drivability really sucks now and it smells more suffer like ever since I put in the new O2 sensor. Exhaust pressure seems stronger and more even than before but the van doesn't idle well and power is erratic now. What would cause the constant .98v? Sometimes it would be at .1 and running crappy after a re-start and then after about 30 sec. it would go back to 8.8-9.5 and smooth out. Ideas?
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PostPosted: Sun Sep 04, 2016 1:18 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure Reply with quote

Super helpful thread--thx!

I ran into some issues while doing the procedure. Wondering if anybody can help.

1. I had trouble keeping it running with the idle control valve disconnected. Although this was done with the van nice and warm, the issue seemed to improve slightly the longer it ran--until i could get a somewhat rough idle with the ICV disconnected.

2. The multimeter readings were all over the place from step one (idle mixture screw adjustment).

3. Moving on to the next steps of getting readings at different RPMs, it was almost impossible to hold the throttle at the middle range RPMs. I could get it to hold at about 2800--anything below that couldn't be held long enough to take a reading.

I'm assuming that my AFM is pretty far out of whack due to the erratic behavior of the throttle response. Any thoughts?

Thx!
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PostPosted: Mon Feb 08, 2016 8:07 am    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Proce Reply with quote

So far I don't have an analog with a 1v range, but I have one with a 10v range that has marks for every .2v from 0-10. I'm getting pretty much the same results as with my digital VOM, except when it is finally steady the analog reads around .6 and the digital reads .8.
Either way, I'm still seeing the voltage dance on the analog that I saw with the digital. Anything below the .6/.8 (depending in which VOM I'm using) and it's all over the place. I got a new digital VOM too because the leads were flaky on my old one but no change.

Maybe it's worth it to find somewhere with a CO meter to get this done right....either that or just put the settings back to what they were before.
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PostPosted: Wed Feb 03, 2016 12:31 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Proce Reply with quote

Roger that, I had to go find an analog VOM with the correct 1V range. They are pretty cheap.
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PostPosted: Wed Feb 03, 2016 12:21 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Proce Reply with quote

Thanks for the help! My O2 sensor is new (<2000 miles), though it's possible I have a lemon.

I think the test leads is the more likely problem and I'll look into that. I have an analog meter too, but the lowest setting is 10v, which makes it impossible to accurately read lower than 1v so I was only using my digital meter. I will test both and see if I notice a drop or any inconsistencies. Maybe I just need new leads for my digital meter.
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PostPosted: Wed Feb 03, 2016 12:00 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Proce Reply with quote

I had a similar problem and I may have a solution for you. My digital VOM was doing that same dance and it did not seem to get better no matter what I did with the CO screw. I hooked up an analog VOM and I found that once in a while, the meter would peg at 0 volts. You will not see it on the digital since it only happens for a moment. The only thing that would cause that would be damage inside the O2 sensor. I replaced the sensor and all was well. My bad sensor wasn't that old and had not been abused, so I'm not sure why it failed.

You should also check your VOM test leads, I worked for hours chasing a "problem" that turned out to be a bad lead.
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PostPosted: Wed Feb 03, 2016 9:23 am    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Proce Reply with quote

The info in this thread is great, but I had a few issues/questions when attempting this procedure. My new engine has a rough/stumbling idle and most of my other options have been exhausted so I'm giving this a shot.

My main question: is the voltage reading from the O2 supposed to be completely steady? What would cause it to go up and down?

The green wire of the O2 and the plug on the valve are disconnected. If I turn the CO screw all the way in it is steady at .8-.9v. It will stay at that spot for another full turn out. But then, instead of gradually decreasing as the screw is turned, it just goes all wonky. After about 1-1.5 turns out, it goes from a steady .8 to going crazy between .1 and .7. So basically I can't get it to remain steady at anything below .8.
Is that a problem? I was hoping to get it steady at a lower reading so I wasn't running too rich.
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PostPosted: Mon Dec 28, 2015 5:14 pm    Post subject: Re: Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Proce Reply with quote

Some excellent info here thanks. We have a 89 2.1 Camper and the AFM has a bent flap and is jamming in the AFM body. I want to disassemble the AFM and see if I can straighten the flap out. Does any,one have an exploded parts diagram of the Digfant AFM that they could post here. Thanks Smile
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PostPosted: Tue Aug 11, 2015 1:36 am    Post subject: Reply with quote

jetpoweredmonkey wrote:
Hmmmm...Alika, assuming you have checked out and found those two AFMs in spec...perhaps there is more going on inside of those little guys than we can discover via the usual checks. I sure would be interested to know if your replacement AFM tidies up the running issues.


Sure is, I left the van parked over the week end, it stopped doing it...

I'm waiting on the AFM, if it runs good or not, I'm gonna send my 2 bad ECU's to be rebuilt so I have some spares. One of them has the ShoeBox diagnostic connector, I'd like to use it Rolling Eyes
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PostPosted: Mon Aug 10, 2015 5:35 am    Post subject: Reply with quote

Applause

This is a really useful discussion! I suspect that the AFM on my Oettinger 2500E has been "tweaked" because the top cover has been re-sealed and there is a tell-tale scratch on the spring tension wheel, from where it has been adjusted by about three notches.
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PostPosted: Sun Aug 09, 2015 11:22 pm    Post subject: Reply with quote

Hmmmm...Alika, assuming you have checked out and found those two AFMs in spec...perhaps there is more going on inside of those little guys than we can discover via the usual checks. I sure would be interested to know if your replacement AFM tidies up the running issues.
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PostPosted: Sun Aug 09, 2015 11:19 pm    Post subject: Reply with quote

As long as you're not too lean, you should be fine I guess...

I swapped back and forth my 2 air flow meters.

I either get a nice idle but extreme bucking if I press the accelerator too much, like I feel I'm gonna loose the engine on the road, or a bad idling,and stalling at idle but nice power when driving.

I ordered a new AFM from Van-Café, besides a used coil, used fuel pressure regulator and used injectors and ECU, everything is new. Man, those injection systems are so much trouble Evil or Very Mad

What I don't understand is prior to the rebuild I did, the engine was happy (rebuilt twice because a head stud snapped while driving Rolling Eyes )

good luck guys!
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