I have a 95 960 that I just purchased. It has 136,000 on it. I bought it from a mechanic that specializes in volvos. This is my first one, and I have questions. He had told me that the car from time to time will get a horrible shake to it, and if it did, then to pull over and cut the car off then back on and it should be fine. It did it last night for the first time, but I have only had the car for 2 days so yeah. I did so and it would drive for awhile then it did it again. This time, it cut off on me and a bit of shake. He had told me that it was possible that the wiring harness needed to be changed, but he didnt wanna invest the (minimum) 1000 dollars to fix the problem. So I got online and have been doing research. One thing I have found is that the engine gets hot and thus could corrode the wires from the heat. One person told me that it wasnt the harness but the coilsprobably needed to be changed. I am at a loss really. But I do have 1 question. If I am able to cut the car off then back on and it runs fine, wouldnt that be a relay of some sort. I was thinking about this after my 4th cut off last night. Please, if you have any idea of what this potential problem is, then give me a shout. Thanks guy

 

What you are experiencing is common, there could be several causes though, but none will cost $1,000.

Remove the black plastic cover on the top of the engine to access the coils and with wiring to the coils. Inspect the wiring for loose insulation, very common to have a bare wire short out by touching the metal of the engine. Also the wires can break internally and cause intermittent contact that engine vibration disturbs.

If that inspection doesn't find anything, then move on to the coils.

It could be a coil, in order to check, the the engine will have to be running bad with the problem.
Access the coils, take out the two bolts that fasten them, then with the engine idling badly, pull one coil out at a time, removing a coil will make the engine even idle worse, but you may get to one that does not change the idle or it changes it very little. It would be safe to say that coil is the cause. Replace with a new one.

Another possible cause is a bad ignition switch, while the engine is running badly, try jiggling the key, does that affect the idle?

Others may have more ideas, let us know you find out.

DanR '94 964 356,000 miles (122,000 on the new engine)

 

MBird, if you are still around, you said that you purchased the car from a mechanic that specializes in VOLVO's, I would think he knows what he's talking about and told you the truth. Other than that, did it pop a CEL? If so, or not, pull codes and post back.