I am on a trip and have trouble...UPDATE

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hi all,

I am traveling with my daughter, helping her moving North, on her '89 Carat, 2.1 WBX - about 80K miles on the engine...

intermittently the vanagon bucks (similar to vanagon syndrome I had in the past) at 3100rpm and 3200 rpm - the AFM has a capacitor - for some obscure reasons the problem disappeared for miles then came back.... no matter altitude or outside temperature, in any gear - the coolant gauge stays steady at LED no more no less.... other than that it runs perfect as a WBX should be...

3 weeks before the trip the following has been done or checked:
- new fuel filter
- new air filter (K&N)
- oil change and new oil filter
- new NGK BP6ET sparks plugs
- new dist cap and rotor
- one year old fuel pressure regulator
- new vacuum hoses
- one year old fuel pump
- one year old coil

the van ran fine till 2 days before the trip the van started to bucks on a 200 miles trip on mountain road and freeway...
so I put in a new Temp2 sensor yesterday... but the bucking problem is still there on and off...

I tried to find out and here are my suspects but please help if you have any ideas..

it could be and I will check:
- throttle position switch
- bad gas
- bad injectors (I use regularly injector cleaner in the gas)
- bad AFM (even with capacitor)

we are in Salinas for one day and will try Van Cafe for help, after that will be in San Francisco - any recommendation for shops, mechanic, what to check etc... are welcome....


many thanks in advance,

dan

Note: to Mark(RubbaChicken)... is this the same problem you had on the Baja trip? if so.. how did you solve it? thanks

[rubbachicken]

hi there dan, it was the throttle position switch on the bottom of the TB
aneasy test i believe is just to unplug it for a bit and drive, if it cures the issue, then you know it's that
also how new is the fuel filter ?
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[Ahwahnee]

The classic test for Vanagon Syndrome is to switch the ignition switch off then on (no need to stop or even slow if you can do this safely on a straight stretch of road). With the Syndrome this action will immediately (albeit temporarily) clear the bucking.

Did you install the capacitor yourself? Was it a tantalum cap? Does it still look securely attached?

This sounds so much like the usual Syndrome that I would pursue that as a possibility early on.

[0to60in6min]

the fuel filter is about 400 miles old.

I install the capacitor myself a 22 microfarad, 35V

I will look at those suggestions

many thanks

[danfromsyr]

check to make sure your O2 wire isn't chaffed, or grounding out
could also try to disconnect the O2 when it happens next time.
_________________

[foolery]

My van would start bucking after warming up every once in a while, and nothing I tried fixed it. After a ton of searching I saw someone else in my situation who replaced their plug wires and fixed it. I tested my wires and they were indeed bad. Replaced them and it's been 2-3K miles with no bucking. Seems like a lot of things can cause Vanagon Syndrome like symptoms.

[davevickery]

This might be a rare occurence but it happened to me and the VW shop knew what it was over the phone.

Exact symptoms but only happens going over bumps, even cracks in the highways would cause it to stumble just for a half second. The tach would drop but wouldn't have time to drop all the way down before it came back up.

Turned out to be the connections on the ECU plug. I didn't have any electronics cleaner or sand paper or anything, so I just undid and did the ECU plug 6 or 8 times and the problem went away for a while. It needed a better cleaner I guess, but absolutely that was causing my symptoms.

I didn't takle any precautions like removing battery strap before doing it, but probably should have.

Worth a shot if yours is happening on slight bumps too.

[tschroeder0]

Take a close look at the three little wires that go to the hall sender in the distributor, the can crack the coating and ground

[0to60in6min]

some more infos...

- I look at the O2 sensor wire, no chaffing
- I look at the Hal sender wires, good condition, no chaffing
- I look a the AFM wiring harness and saw that was tightly pulled down by the big wire loom where it came from. So I pulled that wire loom a bit up and zip tied it to one of the hole in the fire wall and I think it will release some tension on AFM wiring harness.
- it seems to me that the timing is bit off (the idle is not as smooth as I like). I always though it's natural on the WBX... so I may try to adjust a bit..

note: when the bucking happened the tach didn't drop to zero. The bucking happens at 3100/3200 rpm range. If the rpm drops below 3100 the bucking disappear, if the rpm went over 3200 rpm the bucking disappear too.. a headache for me to understand why..

thanks a lot for suggestions,

dan

[0to60in6min]

UPDATE

the mysterious bucking is gone ! - releasing the tension on the AFM harness solved the problem. I think the tension on the AFM harness combined with the harmonic vibrations at 3000 rpm make the contact loose intermittently...

so we continue our trip and stop at VanCafe. They are very very nice folks and they fixed on the spot the odometer that was broken during our first leg of the trip from OC to Salinas. While we wait the odometer I purchase and install a set of spark plugs wires... and that solve the rough idle too....

Peter even gave us a tour of their store and shop.... wow... it's like an Alibaba cavern... now I know that they do repairs too...

and they gave us a bag of cookies...

thanks you all for the help...

dan

[Capulina]

That's funny. I also stop bucking when I release the tension on my hardness.
Bah-dump-bum.

I just woke up and read this and it took me a second to figure out that you meant "harness"

Glad your issue is resolved.