my wife has a 91 740 wagon non turbo.
Yesterday as she was driving it started acting funny. she says she heard like a whining sound. After driving it my self it seems like it has a miss and seems a little louder on exhaust. seems kind of like a miss but does not do it in neutral. only drive and reverse. driving the car there is no loss of power i can detect.
car has 160k miles. Have replaced fuel system relay, tank and main fuel pumps, and noise suppressor relay. Also seems to vibrate when braking but again when in neutral no noise, no vibration. Could this be an exhaust problem??

By the way it's been over 100 degrees for the last 5 days.
Please, Any advice in welcome.

 

a pulsing vibration when braking hard is usually a sign of uneven brake pad deposits on the rotors, or warped disks, and feels much worse if your ball joints or steernig tie rods are loose.

however, it also could be the central drive shaft bearing and its rubber support donut, that would make funky noises and vibrations.

 

new rotors in front 3 weeks ago. new pads all around. also making noise while standing still.

Have been told possible cat converter?? is this possible???

 

a plugged up cat would result in crappy performance at higher RPMs and throttle settings, but not in vibrations when braking.

I'd give that drive shaft center bearing a check out. its smack dab under the middle of the car, halfway between the transmission and the rear axle. it can make all kinda funky noises when the car is moving.

 

Second on pierce's center bearing on the drive-shaft. Titan Joe and I drove around in that 740 for about two years trying to determine if it was knocking or some other suspension related issues. But he thought he'd replace that center bearing, and it all went away.