Noise, Vibration & Harshness or simply NVH. Magazines like Car & Driver give ratings to vehicles based on this aspect of automotive engineering. For example, BMW’s inline Sixes are typically awarded 10/10 for their smoothness. My Volvo would rate 4/10.

I have a ’93 940 Turbo wagon with 186,000 miles on it. In the past 18 months since I’ve owned it, I’ve spent a good chunk of time and $$$ trying to quiet it down and smooth it out. I’ve replaced many parts and not 1 has made a difference.

I would best describe my car’s problem as a buzz or a high frequency vibration. There is nothing violent like a shake or an engine miss. It is a constant buzz that is loud and tiring. The problem is not related to the driveline— its behavior is the same while sitting in Park as is driving at 65mph.

Here is what I’ve replaced in the past 18 mos., 15,000 miles:

Compression Test: 150—145—145--145

Switched to 5W-40 synthetic oil

Tuneup: Cap, rotor, wires (Bougicord), NGK copper spark plugs. Air filter, fuel filter.

Cleaned throttle body, MAF, Idle air control valve.

All vacuum lines with silicone, including brake booster vacuum hose.

Drive belts

Oxygen Sensor

Exhaust System (factory Volvo from cat back)

Engine mounts and trans mount (OE Volvo)

From everything I’ve read here, I thought the engine mounts would fix the problem (they were original and dry-rotted but not collapsed).

A reputable Volvo shop has driven and inspected the car and has not found anything wrong with it.

Driving this car is very tiresome. You have to blast the radio in order to hear it and you can’t have a conversation with someone in the back seat without screaming. The dashboard buzzes. Door panels, center console, etc. rattles or buzzes. The rearview mirror gets blurry from the vibration between 2200-2700 rpms.

I have owned 4 other Volvos (3 240 NA and 1 identical 940 Turbo wagon). All of these were quieter and smoother than this and had more miles.

What am I missing? Ideas?

Chris '93 940T 186K