Hello! Log in or Register   |  Help  |  Donate  |  Buy Shirts  See all banner ads | Advertise on TheSamba.com  
TheSamba.com
 
Vanagon (Digifant) Air Flow Meter (AFM) Adjustment Procedure
Page: Previous  1, 2, 3, 4, 5  Next
Forum Index -> Vanagon Share: Facebook Twitter
Reply to topic
Print View
Quick sort: Show newest posts on top | Show oldest posts on top View previous topic :: View next topic  
Author Message
Pascal
Samba Member


Joined: January 13, 2006
Posts: 792
Location: Fredericton, NB, Canada
Pascal is offline 

PostPosted: Tue Jun 10, 2014 6:10 pm    Post subject: Reply with quote

Since 2004 I've been chasing down my rough idle issues on my 1.9 digijet. I put my new 2.2 in a few weeks ago and the idle was rougher than my tired 1.9 so I've been trying to resold it again and everything tested within spec and I was thinking it's got to be the AFM which also tested within spec except I never thought to mess with the adjustments because everywhere I read said don't touch those adjustments. We'll when I read this post and thought hum, my digitool o2 sensor reading seems to oscillate bellow .5v. When I started this tuning procedure sure enough my van was running too lean and stumbling at idle. The best I could get it with the mixture screw an diddle screw was .45v. But my idle is stable now and wow did that ever wake up my motor!

Thanks you OP for writing such a detailed post and for those of you running digijet, this procedure works with the only difference is we only have 1 O2 sensor wire. What a good feeling to finally dial in my new motor Very Happy
_________________
'84 Westy - 2.2wbx
'91 Cabby
'17 Crosstrek
Back to top
View user's profile Send private message Gallery Classifieds Feedback
atomatom
Samba Member


Joined: May 15, 2012
Posts: 1565
Location: in an 84 Westy or Bowen Island, BC
atomatom is offline 

PostPosted: Wed Jun 11, 2014 10:20 am    Post subject: Reply with quote

Thanks for bumping this thread Pascal - looks like a great write-up and I hadn't seen it - definitely work bookmarking.

You determined to go in to the AFM based on the oxygen sensor reading of .45v, right? What was that reading after you did the adjustments?

I have the surge/hunting idle as well. I need to check the timing before I go deeper, and measure all the grounds. Like the OP though, pretty tempting to just open stuff up out of curiosity, especially when it is locked up with silicone.
_________________
84 Vanagon Westy, 1.9L, California raised but defected to Canada.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Pascal
Samba Member


Joined: January 13, 2006
Posts: 792
Location: Fredericton, NB, Canada
Pascal is offline 

PostPosted: Wed Jun 11, 2014 2:08 pm    Post subject: Reply with quote

atomatom wrote:
You determined to go in to the AFM based on the oxygen sensor reading of .45v, right? What was that reading after you did the adjustments?

I have the surge/hunting idle as well. I need to check the timing before I go deeper, and measure all the grounds. Like the OP though, pretty tempting to just open stuff up out of curiosity, especially when it is locked up with silicone.


.45v was my ending value of the o2 sensor. It was much lower when I started. My screw was out 2.75 turn from fully screwed in. I ended screwing it all in and adjusting the idle screwed to get to .45v. It was a bit like a cat chasing its tail because one screw affect the other.

What this solved was not idle hunting but a stumbling idle or rought idle. I cured my idle hunting a few years ago with a rebuilt throttle body.
_________________
'84 Westy - 2.2wbx
'91 Cabby
'17 Crosstrek
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Skip Laubach
Samba Member


Joined: December 13, 2011
Posts: 237
Location: Elgin, Illinois
Skip Laubach is offline 

PostPosted: Sat Jun 21, 2014 11:36 am    Post subject: Reply with quote

(Digijet) my idle mixture screw seems to be stripped (doesn't tighten or loosen). From original position I turned righty 11 turns and it was loose as a goose, still.

WAG: I wonder if the PO screwed down "below the threads", knocking off some "catch", thereby causing the screw to be turning freely below the female threads. Something like that? I have no idea why the screw appears to be without a female thread match.

Van seems to run fine. Was hoping to "fine-tune".

Not sure that I can lift the idle mixture screw out either. Any ideas? Anyone else experience this?

Many thanks to the OP.

#5 Allen, btw.
_________________
Skip
1984 Westy 1.9 case WBXR Manual (now with 2200cc GoWesty kit)
Since 26 July 2011
Back to top
View user's profile Send private message Send e-mail Gallery Classifieds Feedback
jetpoweredmonkey
Samba Member


Joined: September 20, 2004
Posts: 188
Location: Sacramento, CA
jetpoweredmonkey is offline 

PostPosted: Sun Nov 16, 2014 7:03 pm    Post subject: Reply with quote

This thread should be in a sticky or linked in a FAQ.

I followed this when setting up my GW 2.4 last year, just to dial in the idle CO based on the O2 sensor output. It worked fine for that and I had no need to dive in to the additional adjustments.

Ever since I've had my van, both before and after refreshing the engine, it's always had just a little stumble off-idle, which I put down to the stupid throttle position switch. It's not sensitive enough to get consistent operation if you adjust it too close to the edge, so instead I've always adjusted it to make sure it closes reliably at idle (it's annoying trying to descend a hill with engine braking and not having reliable fuel cutoff). I figured this was the cause of the slight delay/stumble at tip-in, but today I finally stopped to play around with the AFM and discovered that right at the idle position of the air vane, the carbon track was a little worn, and the voltage/resistance would go a little wonky.

I carefully put two small bends into the wiper (sort of a Z shape) so that the contacts would run on a "fresh" portion of the carbon track, and now the voltage (ignition on, reading pins 2 and 4 at the AFM) is a nice linear curve from closed to fully open. And, the tiny off-idle stumble is gone, too. While I was in there, I cleaned the wiper and contact with Deoxit.

Totally worth checking this on your high-mile van (mine has 160K).

Worth noting that, as mentioned in the original post, the RESISTANCE is not linear - however, VOLTAGE with ignition switched on should be. Any bumps or oddities in the voltage curve should be cause for investigation. Use an analog VOM to check this out.
_________________
1991 Westfalia 2WD
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Ahwahnee
Samba Member


Joined: June 05, 2010
Posts: 8327
Location: Mt Lemmon, AZ
Ahwahnee is offline 

PostPosted: Mon Nov 17, 2014 8:39 am    Post subject: Reply with quote

jetpoweredmonkey wrote:
...I carefully put two small bends into the wiper (sort of a Z shape) so that the contacts would run on a "fresh" portion of the carbon track, and now the voltage (ignition on, reading pins 2 and 4 at the AFM) is a nice linear curve from closed to fully open...


Me too. This page (most of the way down) has some illustration of the bends.

Here's my before and after - note the behavior of the arm at idle:


Link



Link
Back to top
View user's profile Send private message Gallery Classifieds Feedback
MootPoint
Samba Member


Joined: September 16, 2006
Posts: 836
Location: Sandia Park, NM
MootPoint is offline 

PostPosted: Mon Nov 17, 2014 10:13 am    Post subject: Reply with quote

Ahwahnee wrote:


Me too. This page (most of the way down) has some illustration of the bends.

It looks to me (looking at the "this page" URL) that he is not so much bending a Z into the wiper but loosening the retainer and moving the wiper down a smidgeon to a "new track over virgin material." I'd be really leery of bending the wiper and then not being able to undo it. Am I paranoid?
_________________
1984 Westy with tencentlife power!
http://www.silverrailsleadville.com
Back to top
View user's profile Send private message Gallery Classifieds Feedback
geo_tonz
Samba Member


Joined: August 01, 2012
Posts: 1464
Location: Courtenay, BC, CANADA
geo_tonz is offline 

PostPosted: Mon Nov 17, 2014 12:35 pm    Post subject: Reply with quote

MootPoint wrote:
Ahwahnee wrote:


Me too. This page (most of the way down) has some illustration of the bends.

It looks to me (looking at the "this page" URL) that he is not so much bending a Z into the wiper but loosening the retainer and moving the wiper down a smidgeon to a "new track over virgin material." I'd be really leery of bending the wiper and then not being able to undo it. Am I paranoid?


Looks bent to me, once angled down right at the base of the arm, then once back up again to get the angle right for both contacts.

Pictures from the page quoted (they also added the red wire which I believe is already on our afm as a black wire).

BEFORE:
Image may have been reduced in size. Click image to view fullscreen.


AFTER:
Image may have been reduced in size. Click image to view fullscreen.



My concern would be getting the tension right. I wouldn't want it pressing so hard it gouged into the track, but I also wouldn't want it to wear a little bit of track off and then start to lose contact.
_________________
VW Logo PUBLIC VANAGON REGISTRY: http://goo.gl/forms/QIiFT0zKhM
---------------------------------------------------
Red Vanagon "Ron Burgundy": 1991 Vanagon Multivan (Weekender) 2.1L Auto - Driver/Camper
Brown Vanagon "Bob": 1985 Vanagon 9 Pass rust bucket. 1.9L Auto - Donor
Back to top
View user's profile Send private message Send e-mail Visit poster's website Facebook Gallery Classifieds Feedback
Ahwahnee
Samba Member


Joined: June 05, 2010
Posts: 8327
Location: Mt Lemmon, AZ
Ahwahnee is offline 

PostPosted: Mon Nov 17, 2014 1:51 pm    Post subject: Reply with quote

Yes, this is something of a 'Hail Mary' 'use only as directed' 'your mileage may vary' 'professional driver on closed course' sort of fix.

I wouldn't have tried it if I didn't already have a spare AFM to install if it all went pear-shaped -- but since I did and since the original AFM was so worn I didn't have much to lose.

I tried to keep the same angle of attack after the 2 bends in the hope that would also approximate the pressure on the track. It took 250,000 miles to wear out the original track so even if my tweak doubles the wear rate I'll be good for a very long time.

You are correct that the site also mentions loosening and repositioning the board but I could not get those little screws loose and I recalled that some have done damage trying to do so on theirs.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
jetpoweredmonkey
Samba Member


Joined: September 20, 2004
Posts: 188
Location: Sacramento, CA
jetpoweredmonkey is offline 

PostPosted: Mon Nov 17, 2014 3:44 pm    Post subject: Reply with quote

As far as I could tell, the board position isn't adjustable nor is the wiper, hence the Z bend. Even if you bend the heck out of it, the wiper is made of such thin metal that it won't be able to exert much pressure on the board. One thing to be careful of is over-bending it and making it run off the side of the contact arc, but it's easy to check for that with the VOM.

Yeah, even if you speed up the wear rate some, it is going to take me a long time to put another 160K on it! It does seem kind of amazing that these last as long as they do.
_________________
1991 Westfalia 2WD
Back to top
View user's profile Send private message Gallery Classifieds Feedback
wtcumby
Samba Member


Joined: September 26, 2010
Posts: 106
Location: PORTLAND
wtcumby is offline 

PostPosted: Sun Jan 11, 2015 4:19 pm    Post subject: Rich/lean? Reply with quote

Image may have been reduced in size. Click image to view fullscreen.


I just changed out my plugs from Bosch to NGK. To me the old plugs don't look that golden brown happy color. Would adj the AFM to run a bit leaner help? How much adj would anyone experienced to know suggest?
_________________
I've got the vanagon fever
Back to top
View user's profile Send private message Gallery Classifieds Feedback
jetpoweredmonkey
Samba Member


Joined: September 20, 2004
Posts: 188
Location: Sacramento, CA
jetpoweredmonkey is offline 

PostPosted: Sun Jan 11, 2015 7:22 pm    Post subject: Reply with quote

The AFM adjustment should be the LAST resort for solving issues like this and only after all other possibilities have been exhausted. If you have reason to suspect it has an issue, run the resistance checks in the Bentley before you pop the lid.

If it were me, I wouldn't touch it, you are likely to add to your problem. Check your temp sender, O2 sensor, fuel pressure, grounds, TPS, and resistances at the Digifant plug first.
_________________
1991 Westfalia 2WD
Back to top
View user's profile Send private message Gallery Classifieds Feedback
wtcumby
Samba Member


Joined: September 26, 2010
Posts: 106
Location: PORTLAND
wtcumby is offline 

PostPosted: Sun Jan 11, 2015 7:36 pm    Post subject: Reply with quote

Thank you. I have my multimeter and Bentley on the ready. I have been slowly going through the vanagon syndrome checklist. Mine van has this syndrome occurring every time the engine reaches operating temp.
_________________
I've got the vanagon fever
Back to top
View user's profile Send private message Gallery Classifieds Feedback
insyncro
Banned


Joined: March 07, 2002
Posts: 15087
Location: New York
insyncro is offline 

PostPosted: Sun Jan 11, 2015 7:41 pm    Post subject: Reply with quote

DigiTool time Exclamation
Back to top
View user's profile Send private message Gallery Classifieds Feedback
wtcumby
Samba Member


Joined: September 26, 2010
Posts: 106
Location: PORTLAND
wtcumby is offline 

PostPosted: Sun Jan 11, 2015 7:50 pm    Post subject: Reply with quote

So far I've done plugs/wires/and cap/rotor. The syndrome is new after I had the coolant system burped and thermostat replaced. I have the 15v capacitor in the mail from allied electronics:

Capacitor; Tantalum; Cap 22.0uF; Tol 10%; Axial; Vol-Rtg 15V

There was quite a mess of coolant which spilled during the coolant bleeding procedure. Could that splashed coolant be the culprit? What's a digitool?
_________________
I've got the vanagon fever
Back to top
View user's profile Send private message Gallery Classifieds Feedback
insyncro
Banned


Joined: March 07, 2002
Posts: 15087
Location: New York
insyncro is offline 

PostPosted: Sun Jan 11, 2015 8:08 pm    Post subject: Reply with quote

wtcumby wrote:
What's a digitool?


Some call it a Shoebox, I call it a Digi.

If you want to guess and spend time and money chasing issues you may not have....go for it...if not, give DigiTool a search and cut to the chase.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
tjet
Samba Member


Joined: June 10, 2014
Posts: 2008
Location: Brea, CA
tjet is offline 

PostPosted: Sun Jan 11, 2015 8:40 pm    Post subject: Reply with quote

Good post. Before cranking on the adjustments, shoot the wiper contact with this first...

http://www.radioshack.com/radioshack-control-contact-cleaner-and-lubricant/6400148.html

My 77 needed a spray every 6 months or so (more so after it's opened)

Instant stumble resolver
_________________
Support the "Right To Repair" bill
https://repair.org/policy
Worth a listen...
https://www.wbur.org/onpoint/2018/11/01/right-to-repair-digital-locks-technology-smartphones-cars
Back to top
View user's profile Send private message Visit poster's website Gallery Classifieds Feedback
jetpoweredmonkey
Samba Member


Joined: September 20, 2004
Posts: 188
Location: Sacramento, CA
jetpoweredmonkey is offline 

PostPosted: Tue Aug 04, 2015 11:14 am    Post subject: Reply with quote

I am back into this thread trying to improve a rough idle on my GoWesty 2.4. It's pretty clear that the issue is related to the AFM adjustments. When I disconnect the O2 sensor, the idle improves. Closing the CO adjustment screw on the AFM all the way REALLY cleans up the idle. I can get a max of about 0.8V out of the O2 sensor with the CO screw fully closed. So, with nothing to lose, I am going to dive back into the AFM and see if I can improve the running some more.

One thing I don't quite understand is the relationship of the O2 sensor to the CO adjustment. With the sensor disconnected, I can run the CO screw in and out and hear and smell the difference in the way the engine runs. Plugging the O2 back in clearly leans the mixture, since the idle is stable (running rich) with the CO screw fully closed, and the O2 sensor leans it and causes it to become a bit more rough. So, does the O2 essentially have a "limit" on the amount of fuel correction? What I mean is, does it only subtract/add "X" amount from the injector pulse time if the mixture is rich/lean? It seems like it would always take the mixture to lambda, but clearly the AFM has an influence, because even with the O2 plugged in, I can hear the CO screw changing the mixture.
_________________
1991 Westfalia 2WD
Back to top
View user's profile Send private message Gallery Classifieds Feedback
jetpoweredmonkey
Samba Member


Joined: September 20, 2004
Posts: 188
Location: Sacramento, CA
jetpoweredmonkey is offline 

PostPosted: Wed Aug 05, 2015 11:35 pm    Post subject: Reply with quote

OK guys, I'm a little stumped here. I popped the lid off of my AFM tonight to see if I could effect any positive change on my stumbly idle. If I unplug the O2 sensor, the idle is just as smooth as you please. Checking the O2 sensor output, all seems normal. Sitting at idle, I can dial the CO screw up and down and get it up to 0.8-0.9V and down to maybe 0.2V. The O2 has a pretty steady output and changes right away when I tweak the CO screw.

With the O2 unplugged and CO set so that the O2 output is about 0.8V or higher, the idle sounds great. As soon as I plug the O2 back in, within a few seconds you can hear the ECU trim the fuel back down and the stumbly idle returns. If I probe the O2 connector while plugged in, I see the normal voltage swinging back and forth across 0.5V.

If I adjust the toothed wheel in the AFM, I can clean up the idle *a little* but it's still not nearly as smooth as with the O2 disconnected. Likewise if I reach in there and manually tweak the position of the air flapper, with the O2 connected I still have that dang lean stumble. The AFM voltage output is nice and smooth with no gaps or drops across its range.

Although the O2 sensor seems fine and isn't all that old (maybe 20-30K miles?), I am thinking about replacing it. I wonder if it's possible that the overall voltage output from the O2 is too low. I guess that's my next move - unless someone else has a better suggestion?
_________________
1991 Westfalia 2WD
Back to top
View user's profile Send private message Gallery Classifieds Feedback
atomatom
Samba Member


Joined: May 15, 2012
Posts: 1565
Location: in an 84 Westy or Bowen Island, BC
atomatom is offline 

PostPosted: Thu Aug 06, 2015 12:22 am    Post subject: Reply with quote

i finally got my idle stable the other week. it took new exhaust headers and some very careful rewiring on the o2 wire and some sealing of air leaks on the air intake boot.

any air leaks and the ECU is going to get more air than it expected. i noticed my aux air regulator (you won't have one on later vans) wire was unplugged. intake boot hoses to aux air regulator and breather tower were questionably sealed.

i cut back the outer copper insulation on the o2 wire. i added a new spade connector and globs of dialectic grease, making sure the spade connector was at least a few mm from the insulation to avoid grounding the signal. new o2 sensor.

the only thing is, i have a nagging feeling that i have less power now, but this is very subjective, and i haven't driven it off the island i live on yet (40km speed limit here, but oh hills). but i have a very steady idle for once and a quiet exhaust. i have a spare AFM i might swap in, i suspect someone went nuts adjusting this one once upon a time.
_________________
84 Vanagon Westy, 1.9L, California raised but defected to Canada.
Back to top
View user's profile Send private message Gallery Classifieds Feedback
Display posts from previous:   
Reply to topic    Forum Index -> Vanagon All times are Mountain Standard Time/Pacific Daylight Savings Time
Page: Previous  1, 2, 3, 4, 5  Next
Page 3 of 5

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum

About | Help! | Advertise | Donate | Premium Membership | Privacy/Terms of Use | Contact Us | Site Map
Copyright © 1996-2018, Everett Barnes. All Rights Reserved.
Not affiliated with or sponsored by Volkswagen of America | Forum powered by phpBB