Engine Bucking intermittently at highway speed

[WM971252]

85 Vanagon, 1.9, I'm getting a "bucking" between 65-70, I've taken it just past 70 and it was bucking pretty good then so I backed off. at 60 and below it seems fine, then again it doesn't seem to matter if it's under a load or not.

Recent work done on it: a Hall Sensor in the distributor went, so it has a new rebuild dist, cap, rotor, wires. Idle stablizer was not hooked up when I got it, I hooked it up when I did this work. Can't really say what's going on in the engine compartment as we're loaded for a flea market and on the road right now.

It almost seems like a governor kicking in, but it's not consistant enough. Before the sensor failure this would exceed the speed limit with no problem.

Any ideas??

Thanks!

[pitbovver]

is there a vacuum advance on the dizzy? My ol' aircooled did this and i had a vacuum leak not allowing proper advance.......$.02

[WM971252]

It is a vacuum unit but they are fine. Once I unloaded I disconnected the idle stabilizer box. The ride back was the same (maybe a little better). It did it to me today at 55.

[Wildthings]

Sounds like your are running out of fuel. Most likely the filter. You can check the fuel pressure under load if you like or just go ahead and change the filter and then go for a test drive.

[AlexWesty415]

This exact problem is happening to me right now, did you ever find a fix? I've tried:

- Changed fuel pump and filter
- Changed air filter
- spark plugs
- distro cap and cables

thought it might be a fuel delivery issue. hen maybe a vacuum leak.
My Tack sars bouncing between 3500-4000(if it's accurate)

[Vanagon Nut]

The tach bouncing could point towards an issue in the ignition system.

There are differences in various model year ignition systems so model year of your Vanagon would be useful.

I don't know if "Vanagon syndrome" would also cause the tach to bounce or dip.

Neil.
_________________
1981 Westy DIY 15º ABA

1988 West DIY 50º ABA

VE7TBN

[PuddleRainbow]

Hello, I had this on my FI beetle and I changed the points, spark plugs, spark plug wires, rotor, cap, injectors and fuel filter along with checking fuel pressure at speed.

Was single injector EV-1 connector with one of the leads pushed up making intermittent connection when the head got hot under load.

Chased for a solid month.

[pdm777]

what was the tach doing when engine misfires???

If it drops suddenly, definately an ignition issue.

My cure was a new coil. No problems after replacing the coil.
_________________
1990 Westy Full Camper

[AlexWesty415]

Dude just put in a new ignition coil. Worked like a charm no more bucking no more tach issues and the voltmeter is reading higher than it was. You're a legend.