I have a '93 VW Eurovan that has started occasionally sputtering at higher RPMs. It will typically start when I’m in 5th gear going down the interstate, and will continue at higher RPM’s in all gears. However if I restart the car, the problem disappears altogether. Sometimes I’ll do the restart while rolling, shift back into gear, and the issue stops. It has been random at this point. Won’t happen for a few days, then strikes again. Car has 270,000 miles, but only about 5,000 with me. Any thoughts?
WAG, Gas filter.
High speed problems often have to do with getting the gas and air into and out of the engine rapidly enough, so fuel filter, air filter, and the exhaust system, esp the cat should be considered suspects. However you’ve got this odd behavior where the problem goes away simply by restarting the engine. So my guess is that you’ve got a problematic ignition module. Cam and crank position sensors , ignition wires, spark plugs, and the ignition coil also a possibility. It may be you are the hairy edge of some kind of an ignition problem, or multiple problems, and somehow it all gets temporarily resolved by turning the engine off and on, but it eventually resumes, possibly due to thermal effects.