I have a 2004 XC90. I have a "come and go" problem that the dealer cannot replicate on his test drives. With heavy acceleration from a dead stop or speed the vehicle will shudder and lunge violently. No problem on slow roll up. When it happens it is difficult to tell if motor is misfiring or transmission is engaging/disengaging under heavy load (6-8 times per second) Dealer replaced transmission 2 months ago and we recently had to replace motor mounts (lunging is VIOLENT when it occurs). The other symptom I think is related is a hissing noise (vacuum sucking?) when cruising at 3500-4000 rpm under load and releasing foot from gas pedal. Sound seems to come from driver side. This sound happens all the time - regardless of whether the car is haveing the shudder fits or not. Finally, a third clue is OBD code 2190 System bank 2 rich. Does this sound like a vacuum leak and how can I find it?

 

Took it to a different dealer and problem diagnosed in 10 minutes. The new motor mounts I got a few weeks ago were not properly installed or fastened. The bolt in the upper motor mount had come completely loose and the motor was flopping around like a fish under load. Apparantly the problem was intermittent because the bolt couldn't fall out completely and sometimes would fall back into the hole and "hold" the engine in place. Whenever the bolt vibrated out of the bracket the resulting engine rotation forward and backward caused the bracket that secures the upper motor mount to punch a hole into one of the air intake castings going to the turbocharger. Thus the noise was not a vacuum but rather the sound of the turbo winding down. And the poor air fuel ratio was causing the erratic acceleration, aggravating the motor thrusting around and causing the check engine light due to bad fuel air mixture.

I pulled receipts and 6 weeks ago I had paid the dealer $417to replace mount (rt lower engine pad part 30741451-6) and $289 to replace cracked upper engine torque mount (part 8671633-9).

I returned the car to the dealer that performed the mount repair work. They, of course had to accept responsibility for the poor quality of their work but called a few hours into it and tried to claim it was my responsibility because the lower "hydraulic mounts" had failed and thats what caused the upper mount to come apart. What a bunch of crap. The way that motor was thrusting under the hood when it acted up no doubt tore up the lower mounts and it never would have happened had they had done the repair properly a few weeks ago.

Never seeing this dealer again...

 

Dealer changed out motor mounts but the problem returned within a couple of days. From dead stop and heavy acceleration, car hesitates like it wants to stall and then all hell breaks loose with rpm trying (sometimes succesfully to shoot to 3500 rpm and something in the transmission (or differential) managing to engage/disengage repeatedly the real wheels and buck the car like a wild bronco. I hate this car....

 

Back to dealer, problem is internal to transmission. Transmission was replaced back in October. This will be transmission number 3. Note first replacement a few months back was at Volvo's expense [Despite the original waaranty expiration] because of the history of failures in this vehicle. Extending the warranty was the one thing they did right but it only happens if you fight for it. The starting point for the converstaion was "You need a new transmission at $7,000" followed by an offer for Volvo to supply the transmission under warranty and you pay for labor to install (~$3000)" Only after escalating to Volvo North America did they concede to do it under full warranty. There are many similar stories on this site and I printed and carried 15-20 of them to the dealer to back up my position. The dealer looks at your service record and how much business he has done with you. I am not sure of Volvo's criteria for extension but they didn't put up much resistance. At least it is clear the new transmission will be covered under the warranty from the replacement - but will it be anymore reliable???