HELP MY MECHANIC CAN'T FIGURE OUT. My 1994 Volvo 850 has a very bad shudder. The front of the car shakes badly when it is in gear and I start to brake or at a stop.
The car idles rough in gear. Fixed one vacum leak. Replaced Idle air control motor, and mass air flow sensor. put o rings in fuel injectors. added fuel injector cleaner to fuel. There is a broken motor mount on right side. I don't this has anything to do with this problem. Mechanic says possible Brake Booster Problem? He was doing process of elimination. I don't know what to do after spending recently almost $1500 on this and other things.
****DOES ANYONE THINK THEY KNOW WHAT MY PROBLEM IS ????
Thank you WildOrca

 

does your parking brake work? If it does, you can easily determine whether or not having your foot on the regular brake is really what causes the problem. Certainly it could be. If the booster is leaking air then you simply replace that. So do that experiment if your parking brake works.


If you parking brake does not work, then do the experiment anyway, but do it with your wheels against a curb. heck, you could just do it with the car pointed uphill, right? If the car still misfires with your foot off the regular brakes, then you're just dealing with an ordinary misfire.

 

Had a compression test been done?

 

You mentioned that you didn`t think the broken engine mount is the problem. My `94 850 had the same problem, and replacing that mount is what fixed it. There`s not much rubber there keeping the whole front of the engine from grinding on the sub-frame. That may not be all of the problem, but I`ll bet that`s at least some of it. Having metal to metal contact there is not a good thing anyway, and could cause other excess vibration problems.

 

There is a difference between a vibration and shaking.

To the OP... Hello? Hello?

 

Yes, there is a difference between vibration and shaking. "Shudder" may be interpreted as somewhere in between.