Hi, I have a 1993 Volvo 940 that seems to have developed a curious problem...for about the last three months, it has started to vibrate at high speeds (60 MPH and over). This all the time now, no matter what the road conditions are like. My first guess was just the car's aerodynamics (it is kind of a big box), but if I press the towing mode button, which disables third gear, the engine revs in about the
4000-5000 rpm range, but the shaking stops.My local mechanic says it is most likely caused by worn front tires, but they were replaced three weeks ago and I have noticed no difference. I don't use premium (91 octane) fuel as the owner's manual recommends, because of the prices I use regular 87 octane, but that shouldn't cause the car to shake at high speeds, right?
The owner's manual also says that low power steering fluid can cause vibrations...I haven't had a chance to check that, but at a free diagnostic clinic the dealer told me that I should never have to add power steering fluid and that it was most likely caused by a bad oxygen sensor -- I know enough about cars to know that that really doesn't sound like the cause.
Any ideas?