Ok so I have had this vibration in this 93 940T. I have changed a lot of stuff. It has made little difference over time, but there have been short term improvements that then seem not to last. Today I talked with a mech who's wife has a 93 940T. She had vibrations. They changed a lot of stuff. It made little difference...etc. THEN; he said there was some notification from Volvo about eeprom in the brain. He had to solder on a new chip into the brain. And, No More Vibration. He says her car, which she still has, has 175,000 mi and looks and runs like new. He is looking at my car now. He said he's been working on Volvos for 25 years and this is the only case like this he ever heard of.
Has anyone heard of this? Also, to me eeprom is flashable, that's the point, but I forgot to ask why he soldered a new chip in. I'll try to find that out tomorrow.