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Vangon Articles - How to Troubleshoot your Vanagon for "Bucking" or Loss of Power Syndrome

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How to Troubleshoot your Vanagon for "Bucking" or Loss of Power Syndrome

August 5, 2014 15 Comments Ask Ken, Fuel system, Wiring Ken Wilford

Why does my Vanagon Buck or Miss and lose power?

Many Vanagons experience a similar problem of bucking, rich running and power loss. This page is to help troubleshoot this problem and determine it’s cause so that it may be corrected.

1. Any and all normal wear items should be checked and replaced if they have excessive wear on them. Spark plugs, plug wires, distributor cap, rotor, fuel filter, oxygen sensor and air filters should all be checked first. If you can eliminate these normal wear items from being a possible source of your problem then you can move on to the next step.

2. After eliminating these relatively cheap wear items as a possible cause of your problem then the next step is to check all of the engine grounds. These are located on the driver’s side head. There should be several small ground straps attached to the head along with a larger ground strap that goes from the head to the firewall under the coil. All of these straps should be there, and the connections should be clean and tight. If this doesn’t fix your problem go to the next step.

3. Next check your ignition switch. There have been times when these have failed intermittantly. Usually a large key chain that is heavy with keys can cause premature failure of this switch. These are only $9 from me and easy to test if they are bad. Simply unfasten the lower cover on your steering column and remove it. Now unplug the black plug that hooks into your ignition switch. Plug in the new switch and start the car using a screw driver (be sure your key is in the ignition and to the “on” position or you won’t be able to steer the van). Now drive the van in similar situations where you were having your bucking problem. If they reoccur then you have ruled this switch out.

4. The next step is to trouble shoot your fuel injection system per the Bentley Manual. The tool you need to do this is a multimeter which can easily be had for $30 from your local Radio Shack. The things that commonly go bad to cause the engine bucking syndrome are:

The Air Flow Meter (located on the plastic air box)

The temperature II Sender (located in the thermostat housing and it has a blue connector on it).

The throttle position switch (located on the throttle valve).

If you need a Bently Manual in order to get the charts to troubleshoot you FI system I have these for sale (part number is LPV800148 in my online store). I could also fax these pages to you if you agree to buy whatever parts you find you need from me. If so please email me with the year of your Vanagon. I encourage you to buy the manual as you will need it for many other things down the road and it is a good investment.

It is possible that you have a problem with some expensive item like your ECU or distributor. If you have ruled out everything else then you can feel better about purchasing a new or rebuilt one of these expensive items. I sell rebuilt ECUs and also new distributors or just the hall unit (which can be replaced in your exsisting distributor). Email or call me at (856)-327-4936 if you need help.

I hope you find this page helpful. If you do please support Van-Again with your parts purchases.

Click Here to look up these Vanagon parts in the On-Line Store.

Comments

Jim Walker January 6, 2020

I have an air cooled 1983 Tin Top. The loose electrical wire was the problem, but you'll be blown away which one it turned out to be. I had a new condenser that I had ordered a while back and randomly decided to install it. When I touched the old condenser one of the wires fell away from it. That was the culprit. Once the new condenser was in place the problem ceased.

josh July 28, 2017

Ive seen bucking in vans caused multiple time by poor quality fuel or water in the fuel. Before spending a bunch of money and time testing components take a sec to remember the basics. Compression, spark and timing, fuel quantity and quality. We recently diagnosed an svx powered syncro that filled up on something so nasty it made the van stop running. No water separation after letting a fuel sample sit overnight. Finally ignited the "fuel" in a test vessel and it would barely burn. Checked it against quality fuel to be sure.

Gw neal April 16, 2017

Hey Jeremy, Did you ever get your van fixed? Was it the AFM? I'm having similar symptoms. Thanks.

Ken Wilford October 28, 2016

Mary, take a look at www.roadhaus.com and see if you can find a good VW shop near you. Could be a simple as needing a tune up. Ken

Mary October 27, 2016

My 95 Eurovan has just today started this bucking. Anyone near Destin Florida who can help? 70 years old and no husband...900 miles from home. Help!!!

DI September 20, 2016

Check if your fuel is flowing good. Should be a heavy stream at tank outlet by the fuel pump. If not remove gas cap, if it flows good then it's something with your vent or/and emissions . I cut a small gap on my gas cap seal, for a quick fix. No emissions in my state. Or I would check the fuel pump after that.

Ken Wilford July 26, 2016

Christuan, Are you sure the van has a good enough level of gas? It sounds like it is running out of fuel. I would try the fuel filter and confirm that it has a good amount of gas in the tank. Then you want to see if it is firing on all four cylinders as that is another reason for the stalling. You can put your hand near the exhaust pipe that is coming out of the head on each cylinder. You should feel the heat (around 700 degrees) coming off when your hand is still a few inches away. If there is one exhaust pipe that seems like it is colder than the others, then that cylinder could not be firing at all and you should investigate that one further. Let me know what you find out. Ken

Jeremy Edmondson July 24, 2016

Christuan, same Vanagon here, very similar symptoms. Just started out of the blue. Starts and idles like a champ. But as soon as I hit the accelerator it stalls out. After first start I can put it in gear and move it around the yard, but seems like once it warms up a little, as soon as I put it in gear it stalls. I just ran out and checked if they AFM was plugged in, thinking hopefully that it was going to be as easy as that, but alas it was all plugged in. Going to run through Bentley AFM troubleshooting tomorrow I guess. Checked vacuum lines, white and purple to the decel valve? that then runs to the charcoal filter, all attached and snug.

Ken Wilford June 14, 2016

Did you just do some work on the engine? I am wondering if your Air Flow Meter is plugged in? I have forgotten to do this a few times and it acts the way you are describing. Idling at 2000 is not correct either. It should idle at around 900-1000 rpms. I would check for vacuum leaks, and if that isn't an issue check your idle adjustment screw on the throttle body and check to see if your throttle position switch is functioning properly. If those things are right then your Idle Control Unit is probably bad and we have those rebuilt if you need one. Let me know what you find.

Christuan June 12, 2016

Have a 86 westfalia, 2.1 waterboxer. Start great, rev at 2000 rpm ans comes down gradualy as engine warmed up. After running 2-3 min idle comes back up slowly to near 2000 rpm and it dies instally as soon as you try tu accelerate. Restart like a charm, at first idle is fine but cycle recomes after 2-3 min....

Ken Wilford January 8, 2016

I have been asked to do a video for the rebuilding of the waterboxer a few times. The problem is that I don't really have the time to do it. I think the best way to get this project done would be to start a kickstarter campaign that raises funds for me to do the video. When enough money is raised, the video is made and backers get the video first. Otherwise, not sure when, if ever, I will get around to it. It is just a matter of taking the time to do it. I know my friend Bob Donalds talked about doing one of these How-to videos for years. Just never got around to it because he was so busy. If you are interested in helping fund this project as a kickstarter, let me know and we can go from there. Ken

Nick January 7, 2016

Looking at rebuilding a 2.0 water boxer 1987 Vanagon motor but can't find any videos on how to rebuild the motor or any helpful hints. Any suggestions or best videos to watch? Thank you

Ken Wilford March 14, 2015

I just looked over the article again. The advice given can also help early Vanagon owners as well. Vanagon Syndrome is just another name for bucking, rich running, etc. All Vanagons can have those symptoms. If you are experiencing this symptoms with whatever year fuel injected Vanagon, follow my advice and it will help you find the source of the problem.

Steven D. Johnson March 12, 2015

Would you please confirm the Vanagon Syndrome symptoms you are referring to are limited to post-1983 model years using water cooled, D-Jet fuel injection, or does the Vanagon Syndrome also affect the 1980-1982 air cooled models using L-Jet?

luke lucas December 13, 2014

thank you only obe year exper My first Vanagon a $2000 dollar education. Better then a college course I learned hands on with online help from you and other online groups how to take a $350 junk yard special apart and rebuild (I hired a pro to horn cyil and install new rings) other then a guy spraying Alk-200 & 201+ I did all the work added hardwood floor and custom interior. This weekend is my first road trip and I promised my girlfriend I will be home for christmas Fryeburg Maine is only 3,500 miles Wish me luck Happy Holidayz gypsieband64@gmail.com

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