New Vanagon owner; possibly chasing the 'highway hiccup'

[ThrowerVan]

Hey everybody. We recently picked up an 86 van, and are super excited to make it our wonderful adventure vehicle.

Last weekend we were planning on taking it over to the coast for some 4th of July fun, but I think I may have the dreaded 'highway hiccup', and I just want to verify, and hopefully get some clarification on the guidance I've seen throughout the forum while researching it.

Here's the scenario: Driving for about 15 minutes, engine nice and warmed up. Get up around 60mph, and 'hiccup'. RPM gauge drops a ton (from 3k to maybe 200), van bucks like it ran out of fuel, then it picks back up. This either doesn't happen for another few minutes, or it happens immediately after. We drove around for a half hour or so, and towards the end it started to get really bad. It would happen at lower RPMs as well, making it a very annoying and stressful drive home.

Is this the dreaded vanagon syndrome?

In searching the forums I've seen that the 2 most likely culprits are the AFM and the hall sensor. So today I started doing some inspection.
I don't really know that I can tell what a bad hall sensor actually looks like, and I'd like some guidance on how to actually test it (if that's even possible). A new one is $150 bucks, and I'd rather not just throw unnecessary money (did that with a VW rabbit I had back in the day, and it was a mess).

Anyway, I also started to look at the AFM. Is there a best way to take the cap off the sensor? Or do I just cut the glue and pry the bugger open?

In looking at that, however, I came across this little gem:

Now, I may not be an electrical wiring maven, but this seems a little.....wrong

I've read about attaching a capacitor to help even out the signal from the AFM, but is this even installed correctly?


Anyway, I love this forum, and so far, even though it's causing a few issues, I love my van!
Thanks in advance for any and all help/advice.

-Scott

[Californio]

My experience putting in a capacitor was that it worked for a while, but then I had to get a new air flow meter.

Why don't you try soldering that capacitor back in place and see if the problem stops?

[ThrowerVan]

[djkeev]

[Ahwahnee]

How I attached mine...

Though you may be able to get away with just reattaching it as you describe (not too pretty though).

Since it is there already it seems very likely the PO experienced this problem too - good that there is an easy fix.

PS - Just checked, I installed the cap 14 years ago and have had no stumble since.

[bobbyblack]

Ahwahnee's pic's tell it all, and clean too! I have a pouch of the tantalum capacitors in my stash, if I were closer, I'd offer up whatever I could. Vanagon Syndrome killed my sister's enthusiasm.. she had an '89 that she just couldn't deal with any more and let it go. That was before my T3 days -- only had experience with Transporters in T1, T2, and T4's at that time... Finally "graduated". Now there seems to be a growth of them on my hill..

Here is what VW thought people should purchase...

(not my advert, but this is 'the fix')
https://www.thesamba.com/vw/classifieds/detail.php?id=2458489

It just has a capacitor somewhere in there, I guess..
_________________
'87 Westy 'Flossie','86 Westy 'R1','86 tintop GL - Subi2.2 'J2','83.5 stock tintop L 'ZoomBus','74 Karmann Ghia, '63 Notch

[ThrowerVan]

Interesting!
I initially thought the second bit of solder was just a lazy repair to a broken wire, but it's actually where the other leg of the cap goes.

I like you how did yours Ahwahnee, I think I'll most definitely make it a far more tidy repair than it is, preferably with some kind of support so it the joint doesn't move as the wire bounces around, or tuck it inside the AFM like you did.

That pigtail is interesting. Does anyone know what is so special about it? Perhaps you're right Bobby and it does just have a capacitor in there all neat and tidy.

Any tricks to getting the AFM open? I'm thinking a razor blade to cut the adhesive? What about putting the cap back on? Perhaps just regular silicone?

[pdm777]

I chased this intermittent 'cut out' for months.

The tach dropping is one of the hallmark signs.

In my case, I replaced the ignition control unit,
the coil, and new ground cable.

Haven't had an issue since then.
I am guessing that when the coil gets HOT
it fails. Never happened when not Hot.

This can drive you crazy!
not sure if Anyone has found the Answer.
_________________
1990 Westy Full Camper

[4Gears4Tires]

Isn't the tach dropping a loss of timing data from the computer?

That wiring looks terrible. Definitely resolder that. Liquid electrical tape could work nicely here.
_________________
'87 Syncro
Ferric Oxyhydroxide Superleggera Edition

[ThrowerVan]

Just to give and update and possibly some closure to this: I resoldered the leg of that capacitor, and now all is good!

However, I would definitely like to move its location to a place that doesn't wiggle and vibrate. So I'll be putting it in the AFM case.

My next question: I have been searching for a new capacitor, and have found a bunch of potential options, but I don't know enough about electronics to know exactly what I can or can't put in there.

Would this work? https://www.mouser.com/ProductDetail/AVX/TAP106K020GSB?qs=D60Q9NgkslkWRPqD6OZnKA%3D%3D

Also, I'm pretty sure I won't be able to get in to the AFM without destroying the cap, so I'm going to model one and 3D print a replacement. I'll put the file online and post it in the 3D printing thread when I get it designed



And finally, I ran across a thing on the internet where you can move the needle of the AFM to a fresh patch of the resistor trace, and was wondering if anyone has done this to our AFMs (this one was for a Bosch AFM on some other random vehicle).

[Abscate]

If you guys firm up the specs this cap , I’ll order 100x and ship to people for free on request via usps. I do the same for diodes for SAS deletes , too.
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.ssS!

[Wildthings]

I was able to install the capacitor in the "Vanagon Syndrome" wiring harness that VW sold. Worked out just find. I think you could also install the capacitor in the plug for the AFM with some thought. On my 91 the lid of the AFM had never been removed for the 240K miles that were on it when I replaced the 2.1L with a Subaru.

I did install the capacitor in the AFM of my 1.9L as the lid had already been removed. I drilled a teeny hole in the brass arm running out to the moving contact to hold the leg of the capacitor in place while I soldered it. 1.9L engines don't get Vanagon syndrome, but the capacitor cleans up the signal being sent to the ECU making for a much smoother idle.

[ThrowerVan]

Found these on Amazon. I'm going to pick them up, and see if they work, and hopefully remember to report back.

https://www.amazon.com/gp/product/B07TXYWN5L/ref=ewc_pr_img_1?smid=A37QXIKGEOBCOK&psc=1

[Wildthings]