Engine shudder

[Blackbear]

I have a 2002 xc70 w/120K with an very strong engine shudder I think that it is the coils but not positive. My wife was driving home and all of the sudden she said the engine began to shudder and then there was a bad burning smell. I went out started it up and it was shuddering/pulsing at idle and in gear. The one thing I curious about is that the RPM's held constant and I am not getting a check engine light. I do have a code reader but without the light going on I have only a hunch to go by. Do the coils fail without any indication and would the RPM hold constant even if the Cylinders weren't firing?

thanks and I love this site.

[greemero]

When I had a coil go out, it never threw the check engine light. But my problem was intermittent, and we never noticed it at idle, only at speed when you would accelerate.

I would think if yours is doing it all the time, and a coil was the culprit, you should be getting a code, but I think I recall reading where others didn't get a code either.