I am re-posting to clarify the symptoms that my car is exhibiting.
I have a 97 850 non-turbo wagon that is intermittently "shuddering" and even "bucking" at 55-70 MPH. It is so severe that I'm afraid the car will even stall. Sometimes it is a little flutter, other times more severe.

There are no error codes in the computer and my usual mechanic who is excellent is stumped. I am taking it into the Volvo dealer this week but wanted to gather ideas on how severe this problem might be before going.

Could this be a fuel pump or fuel filter? Something electronic? Transmission?

Any and all ideas GREATLY appreciated.

Volvogrl,
Did you find the cause of your problem yet? I'm curious because I have similar symptoms on my '96 NA wagon. The problem is intermittent and I have not been able to reproduce it for the dealer.
Are you having any 'rough idle immediatly after starting' problems? I have this symptom and am curious if it is related to the shudder at speed.
Thanks,
hillm

hi hillm -

The Volvo dealer still can't figure it out. They claim there are no codes stored in the engine. They've tried everything - $500 worth of labor. Tried a new fuel filter, but that didn't work either. It sounds like the fuel pump relay may be the culprit, or serious trannie problems.

If anyone has any other ideas, please let me know.

volvogrl

I have seen a flaky coil cause that.

When this happened a couple years ago in a Volvo I was test driving, I slowed down to 50-55pmh and then manually downshifted to third for a couple seconds, then back up to normal. Problem stopped....until the next restart. (Of course, I suspected a transmission problem and passed on buying that particular vehicle.)
--


David
1998 S70 T5SE // misc mods (mostly lighting) // red calipers
1992 940 GLE // Hella Micro DE foglights and 170K

When it starts this "shuddering & bucking" at 55-70 mph can you drive through it to 75-80+ mph and it goes away? Or will it not accelerate through this shuddering? If it won't accelerate through it and on up to 80+ mph with no problem then I would look at the fuel filter, change that and see if it goes away. If it WILL accelerate out of the shuddering and on up to 80+ mph and smooth out it might point to a transmission problem, possibly the torque converter locking and unlocking out of step with the rest of the tranny. I've had the problem where it would not accelerate through it and it was the fuel filter. Good luck ........ Mike

dear volvogrl:

heard a similar prob being discussed on car-talk once. one suggestion by the bros was to check all important wiring harness and electrical contacts (ESPECIALLY THE GROUND CONNECTIONS) near the battery, alternator, engine computer, and engine chasis, fuel pump, etc. also check if your fuelfilter needs to be changed. good luck

yt850
'94 855, 20v, na, 5spd at 85k

Given that nobody responded to your last post--that means to me that nobody knows what is wrong. Your best bet is to let the dealer diagnose it, after all, they sell them. They are more apt to know it when they see it.

850-Rick in Denver