THE FREQUENCY: This is a condition that has become progressively worse over the last six months. Initially it occurred once a week and now it is happening almost every day, lasts longer and is more acute.
THE SYMPTOMS: Initially and randomly, while driving at any speed, the car would begin to hesitate as if it might stall but did not- The hesitation was much like a shudder or power loss. At this time the check engine light would blink and stay on for a couple of days. This whole event would last less than a minute and the car would return to normal until the next one.
Now, six months later, it is occurring almost every day. At startup, at low speeds, at stop lights… A LOT!
WHAT HAS BEEN DONE SO FAR: After frequent and unsuccessful visits to the Volvo Dealer all the plugs, the wires, the cap, and the rotor have been replaced with no luck.
The dealer says the code indicates a misfire on the #3 cylinder.
Did they swap the injectors to rule them out. They also need to run a compression test. Could be a bad head gasket.
Time to find a better shop
If they can’t diagnose a problem that is occurring all the time, they shouldn’t be working on your car
The next shop, NOT THESE GUYS, need to do a fuel pressure test and an injector balance test, in addition to that compression test that @knfenimore mentioned
FYI . . . a flashing check engine light means a misfire which is so severe that it is damaging your catalytic converter
It might already be partially plugged, which would explain the lack of power
A back pressure test could give you some indication as to the cat’s condition
Bad ground connections in the engine area can cause things like that to happen. I suggest you clean all the grounds you can get to along with the battery connections. If that doesn’t help then perhaps there is either an ignition or fuel delivery problem. A bad fuel pump perhaps or power connection to the ignition system. Changing the fuel filter may help. Do the simple things first.