My buddy is currently having issues with his 2006 s60 2.5T. We just drove it back home from 2 hrs away after he blew a tire on the interstate, and it’s having a bad misfire.
So to start the story off after we got it home, I took the car into work early to get the tires changed (I work at a tire shop) and on my way there it had a really bad hesitation when I was trying to get up to speed. When I was finished putting on the new tires, I went to take it for a spin to test out the new tires and the cel came on. My buddy has a code reader in his car, so I hooked it up and sure enough it had a p0302 cylinder 2 misfire. So I promptly turned around and shut it off. Once I was done with work and got it back to his place it was throwing p0300 random cylinder misfire code and the p0302. And thus the frantic diagnosis ensued..
First we tried swapping cyl 1 and 2 coil packs to see if we could get the miss to follow the coil pack. After clearing the codes and starting it back up, not only did cyl 2 still have a misfire, but cyl 1 and cyl 4 threw misfire codes. I was kinda bewildered by that, but we put the coils back in their original places and replaced cyl 2 spark plug with a brand new one which had no effect. We then tried swapping cyl 3 coil pack to cyl 2 since that cyl so far had no issues, and it didn’t provide any useful results either, just random misfires on 1, 2, and 4 being sure we clear codes before each test.
After that, I was kind of at a loss so I started thinking about fuel system stuff and tried putting in a can of seafoam into a half full gas tank for a strong concentration that could clean a potential blockage in a fuel infector. That didn’t help either, but we may need to give it some time to sit in the fuel system to really break down any gunk in it.
So now I’m starting to go to worst case scenarios. Could the head be cracked? Is the compression going to be in the ****ter on one of those cylinders if we do a compression test? My buddy is not car savvy at all and also very broke so if either of those things prove true it would pretty much be a death sentence for the car being under his ownership. I’ll admit our testing process was not perfect, we really should replace all the plugs and coils to completely eliminate that as a source of a problem, especially since the car has 114,000 miles on it and the plugs are original to the car. But before he starts throwing money at parts I wanted to make sure there couldn’t be another issue I’m just not thinking about. Any ideas from the forum?