The only other time I have replicated the problem in a different gear is driving up steeper inclines in 3rd gear and trying to get above 40-45, or 30-35 depending on said incline. However, this was prior to the bucking starting on flat ground around 60mph. The mechanic who inspected Penny when we bought her informed me that this bucking had been an issue they had not been able to figure out after weeks of exploration in the shop. Just so it's out there, she was a CA van in her previous life and they thought maybe it had to do with a relay in the emissions equipment from CA. As an additional note, mpg has dropped from a pretty consist 17-19 on the highway and through hills to somewhere around 11-13.
As far as diagnosis, I'm pretty new to understanding engines and mechanics, so bear with me here. Listening to the engine, it does sound like I have a vacuum leak (hissing), seems to be near the distributor, but I could be wrong. I've replaced the idle retard vacuum hose, which did seem to lower the rpm at idle. I need to find where the vacuum leak(s) is/are, and I'm nervous about spraying anything flammable near that spot without someone experienced with me
![bom :bom:](./images/smilies/bom.gif)
This past summer another vanagon owner helped me out some and identified through looking at spark plugs that it was running lean. We also checked the timing and it was looking good. I adjusted the gear in the AFM about 5 clicks counter clockwise to richen the mixture, but haven't done any further checking of spark plugs yet, and I didn't adjust anything else at that time.
I'm not positive when the fuel filter was last replaced. It's been suggested that I replace that as a start to see if it fixes the bucking. I'm going to order one of those this week.
Alright - into the rabbit hole I go! Hopefully, with your extensive banks of knowledge and guidance, I will be successful in learning
![salute :salute:](./images/smilies/icon_salut.gif)