My 1998 Subaru wagon with 140,000 miles vibrates when stopped at a stoplight. If I shift into neutral, it stops. The dealer said a mechanic at their garage has the same problem with his “older” Subaru and can’t find a cause. What could be making it do this?
Idle too low or possibly too high, engine or transmmission mount, or an engine performance problem due to a vacuum leak, low cylinder compression, ignition fault (wires, plugs, etc.).
Depending on the definition of the “older Subaru” the causes can vary but if the engine itself and the ignition end of things is fine then odds are it’s related to a mount or an idle speed being too low. Mount problems are rare so you might compare the idle speed (brake depressed, transaxle in DRIVE) to the figure listed on the sticker underneath the hood and see if it’s lower than what the sticker says.