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kirkvw72
Samba Member
Joined: March 27, 2006
Posts: 272
Location: Hoffman Estates, Illinois
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 Posted: Mon Jul 06, 2015 7:47 pm Post subject: SOLVEDish - Old Fuel Filter, stumbling. Adjust AFM? Fuel Sta |
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I am on a road trip from Chicago to LA and back that I have posted on elsewhere. I have my wife, 3 year old and 6 year old with me.
Van is a 2WD, 1987, 2.1. Has the VW AFM "vanagon syndrome" cord. New AFM last year. VSM. Fuel filter is 3 years old. I've never changed the fuel pump.
On the way out, my fuel pump got loud in Albuquerque (6000ft) and the van gave one stumble. 1/2 tank of gas at the time. I filled up, and it didn't come back.
Today, while climbing out of Salt Lake City (We are heading home on I80), I felt like I had reduced power, and had several "single" stumbles and a couple multiple ones. I'm at 6700 feet now. Tank was about 1/2 full. Tach doesn't move, which leads me to fuel delivery.
Idles normally. If I brought it much over 65, then it would give me a little stumble. If I kept it at 60, it was fine.
The van ran perfectly all day before this and averaged 22 mpg.
I have a spare fuel pump and a spare filter that I could install tomorrow morning.
OR
Do I need to adjust my AFM for the altitude?
Is there anything else I should do or look for?
Thanks in advance.
_________________
2015 VW GTi Autobahn
2000 Mercedes Benz E430
1992 Miata, automatic converted to a 5-speed
1988 Vanagon Wolfsburg
1987 Porsche 944 (951) Turbo
1987 Vanagon GL, Rocky Jennings Heads, RMW Exhaust, ASL 5-speed, AMG Wheels
1981 Porsche 924 (931) Turbo
1972 Beetle (standard)
Last edited by kirkvw72 on Tue Jul 07, 2015 6:35 pm; edited 1 time in total |
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idahoskier
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Joined: March 30, 2009
Posts: 161
Location: Donnelly, ID
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| Posted: Mon Jul 06, 2015 8:38 pm Post subject: |
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How old is the gas tank? If its original then its probably sending crud down the line. You most likely have a filter issue so just replacing that should remedy the problem. I would try just the filter and keep the pump as your spare. When you take it out try and blow through it and compare to the new one.
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85 Westy w/ 2.2L Subaru
91 Westy w/ 2.5L Subaru - sold |
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kirkvw72
Samba Member
Joined: March 27, 2006
Posts: 272
Location: Hoffman Estates, Illinois
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| Posted: Mon Jul 06, 2015 8:40 pm Post subject: |
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| idahoskier wrote: |
| How old is the gas tank? If its original then its probably sending crud down the line. You most likely have a filter issue so just replacing that should remedy the problem. I would try just the filter and keep the pump as your spare. When you take it out try and blow through it and compare to the new one. |
Idahoskier - Thanks for the quick reply.
Unfortunately, I do not know the age of the tank.
I'll start with the filter. Can't hurt anything.
_________________
2015 VW GTi Autobahn
2000 Mercedes Benz E430
1992 Miata, automatic converted to a 5-speed
1988 Vanagon Wolfsburg
1987 Porsche 944 (951) Turbo
1987 Vanagon GL, Rocky Jennings Heads, RMW Exhaust, ASL 5-speed, AMG Wheels
1981 Porsche 924 (931) Turbo
1972 Beetle (standard) |
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idahoskier
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Joined: March 30, 2009
Posts: 161
Location: Donnelly, ID
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| Posted: Mon Jul 06, 2015 8:51 pm Post subject: |
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You can also cut it open to see what the filter has caught 
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85 Westy w/ 2.2L Subaru
91 Westy w/ 2.5L Subaru - sold |
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jismay
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Joined: February 02, 2010
Posts: 219
Location: Norco, CA
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| Posted: Mon Jul 06, 2015 9:14 pm Post subject: |
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Not quite the same situation, but I developed an issue with stumbling/bucking on my 1980.
My problem ended up being resolved by cleaning the AFM tracks with contact cleaner. I was getting enough contamination on the tracks that at certain loads/wiper locations it would get a bad reading. The cleaning fixed the problem, and so far it has not come back.
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1970 Squareback with 1915cc dual 40idf
1979 Beetle Convertible
1980 Vanagon Westfalia
1989 VW Cabriolet |
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0to60in6min
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Joined: November 27, 2006
Posts: 3416
Location: OR & CA (Oregon/California)
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| Posted: Mon Jul 06, 2015 9:23 pm Post subject: |
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the OP has one year old AFM and the harness...
so it narrows down to fuel starvation - I would put in a new fuel pump and fuel filter and a new fuel pressure regulator... |
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crazyvwvanman
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Joined: January 28, 2008
Posts: 9923
Location: Orbiting San Diego
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| Posted: Mon Jul 06, 2015 10:24 pm Post subject: |
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Change the filter. Then see if that takes care of it. Buy another spare to carry, always.
I recently drove my 87 from Calif to Florida. Bought bad gas in NM. Did a slight stumble at highway speeds, getting worse as
I went. Changed the filter in Texas. That was 7,000 miles ago.
Mark |
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djkeev
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Joined: September 30, 2007
Posts: 32584
Location: Reading Pennsylvania
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Ahwahnee
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Joined: June 05, 2010
Posts: 9798
Location: Mt Lemmon, AZ
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| Posted: Tue Jul 07, 2015 6:12 am Post subject: Re: Help Please. Adjust AFM? Fuel Starvation? Pump? Filter? |
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| kirkvw72 wrote: |
| ...Do I need to adjust my AFM for the altitude?... |
And just so you're not tempted (to make things worse) -- no need to adjust the AFM for altitude.
I've driven from -282' to 14,439' w/o adjusting anything. |
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Hybrid VW
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Joined: May 03, 2014
Posts: 128
Location: Central Oregon
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| Posted: Tue Jul 07, 2015 6:59 am Post subject: |
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Another "can't hurt" fix that was suggested to me by a local mechanic that has/had a syncro, is to run a grounding wire from the body of the AFM to a good ground (I went to the cylinder head right below it).
Apparently, VW issued a service bulletin about static electricity building up inside the AFM and causing some stumbling/hesitations. The issue would go away when you cycle the ignition. I haven't driven the van any distance since I added the wire, but I can't see it hurting anything. |
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kirkvw72
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Joined: March 27, 2006
Posts: 272
Location: Hoffman Estates, Illinois
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| Posted: Tue Jul 07, 2015 6:34 pm Post subject: |
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Solved...ish
Filter change noticeably improved the power and consistency of the van.
Possibly related, I got my best MPG's of the trip this morning after the filter change; 23.68. It also was high 50's-low 60's and very little wind. Set the cruise at 65mph. The van was purring nicely!
There was a major downpour in Laramie, WY. Crazy amount of rain; it was washing down the highway. Got a good stumble; guessing it was water getting up on the o2 sensor (even with the RMW SS exhaust).
Between 8000-8700 feet, I also had several very minor stumbles.
Had one more small one towards the end of Wyoming. Filled up with 100% gas and had no more the rest of the drive today (140 miles).
_________________
2015 VW GTi Autobahn
2000 Mercedes Benz E430
1992 Miata, automatic converted to a 5-speed
1988 Vanagon Wolfsburg
1987 Porsche 944 (951) Turbo
1987 Vanagon GL, Rocky Jennings Heads, RMW Exhaust, ASL 5-speed, AMG Wheels
1981 Porsche 924 (931) Turbo
1972 Beetle (standard) |
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djkeev
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Joined: September 30, 2007
Posts: 32584
Location: Reading Pennsylvania
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kirkvw72
Samba Member
Joined: March 27, 2006
Posts: 272
Location: Hoffman Estates, Illinois
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| Posted: Tue Jul 07, 2015 6:40 pm Post subject: |
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I agree that something is still up, but the lack of power is fixed.
Surprisingly, I think it is vanagon syndrome. Has only stumbled after hours of driving. It is very brief. It goes away.
The ignition switch is only a year old, fyi.
The VW AFM cord I installed was used; certainly could be faulty. I'm tempted to take it off.
Would a BusDepot rebuilt AFM have a capacitor installed (that's where I got it from)?
_________________
2015 VW GTi Autobahn
2000 Mercedes Benz E430
1992 Miata, automatic converted to a 5-speed
1988 Vanagon Wolfsburg
1987 Porsche 944 (951) Turbo
1987 Vanagon GL, Rocky Jennings Heads, RMW Exhaust, ASL 5-speed, AMG Wheels
1981 Porsche 924 (931) Turbo
1972 Beetle (standard) |
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Wildthings
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Joined: March 13, 2005
Posts: 50337
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| Posted: Tue Jul 07, 2015 7:47 pm Post subject: |
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I wouldn't count on a rebuilt AFM being in perfect condition. I have seen AFM's where the rebuilder had done nothing more than clean the exterior, maybe do some minor testing, and then slap their sticker on it and then shove it in a box and ship it off.
You could be looking at a bad ignition or fuel pump relay, a bad ignition switch, or the wiring to your Hall sensor giving out. Could be other electrical problems as well, hard to trouble shoot until it gives out totally. |
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morymob
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Joined: November 09, 2007
Posts: 4683
Location: east-tn
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| Posted: Wed Jul 08, 2015 5:35 am Post subject: |
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| Since it ran good until the big rain, give it a chanceafter it dries out , if ok then work out the wet problem. |
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Ahwahnee
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Joined: June 05, 2010
Posts: 9798
Location: Mt Lemmon, AZ
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| Posted: Wed Jul 08, 2015 6:38 am Post subject: |
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| kirkvw72 wrote: |
| ...Surprisingly, I think it is vanagon syndrome. Has only stumbled after hours of driving. It is very brief. It goes away... |
In my experience the Vanagon Syndrome does not go away once it begins unless you switch off and back on.
Still, easy enough to add the capacitor to the AFM if you want suspenders and belt protection. |
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