Assuming this issue did not happen after recent work you did.....

My first thought is "check for a vacuum leak".

I've read that spraying starter fluid or even WD40 (WD40 safer to
use?) on suspect vacuum hoses, intake boot can be revealing. Idle is
affected if the spray is sucked into the intake.

I was curious about the WD40 use. One comment online suggested that
using it may harm the O2 sensor. Not sure if poster meant that "too
much" or "any" amount of WD40 would do this.

There should be info in the archives on this vacuum leak check method.

Neil.

On Fri, May 27, 2011 at 5:51 AM, John Lauterbach
<jhlauterbach@bellsouth.net> wrote:
> My '84 Vanagon is exhibiting some strange symptoms. �Engine is Boston
> Bob 1.9L installed 9/2003 and everything that I could buy new to go with
> it I did. �Also recently changed rotor and distributor cap and made sure
> there was no corrosion at connection between spark plugs and plug wires.
> Timing is right on and idle is around 900 rpm. With van warm and going
> up slight grade with automatic transmission in "high", engine will
> sometimes run roughly. �I never had this problem before. �Is there a
> solution other than throwing dollars at the problem with new plugs,
> wires, O2 sensor, etc.?
>
> John
>

-- 
Neil Nicholson '81 VanaJetta 2.0 "Jaco"

http://tubaneil.googlepages.com/

http://groups.google.com/group/vanagons-with-vw-inline-4-cylinder-gas-engines