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Hello Swedespeed community, thanks for drifting to the new guy's thread. As the title says, I'm having a misfire. It seems complicated. Just picked up this 2005 s80 2.5t about a week and a half ago with 165k miles on it. 2 grand, it ran and drove fantastically, and was for my girlfriend buying a car for herself. I told her I thought it was OK, so we got it. no problems for at least an entire week. The guy who sold it to us had a dealer's license and showed us that it had been purchased at auction from carmax, apparently it was unpopular and sat on the lot for a long time.

Took her to the concert at the houston rodeo the other night, probably the longest drive the car has seen in awhile. Sway bar bushings need replacing, check. Drove about 45 minutes to that side of town with no issues, car sat for a few hours, then we drove about an hour to get home (traffic getting out of there was baaaaad.) As soon as we got off the highway and onto a 35mph road, I felt a misfire that seemed constant but minor, so I figured it was the plugs. After all, I had not changed them yet.

So, the next day I picked up 5 new plugs and went to gap and install them after getting the codes read. Cylinder 3 had the misfire (also p0497, evap purge solenoid i think), so I swapped coil packs around while installing the plugs just to see if the problem jumped around in case it wasnt the plugs. What to my surprise, It didnt fix my issue, made it worse. Code reader reads codes for misfires in all cylinders and random misfire. Great, cant rely on codes to find my issue. So, I get to work testing and diagnosing.

First of all, replacing all the original equipment in original locations before I even started cannot recreate the original cylinder 3 misfire. So, I looked into it all. I am able to completely disconnect cylinders 1 and 2 coil packs while the engine is running with no changes in behavior. So I shift all coil packs and plugs down 2 cylinders, and same thing. Problem has not moved with plugs or coil packs. So I run a compression check. I know it should be close to 200, but all cylinders read evenly at 90-100psi. So I think, not a gasket or cylinder leak issue. All injectors ohm out the same and I rented a noid light to test PCM signal puls to injectors. All is fine with the noid light. Then, I start to spray carb cleaner everywhere looking for that surge in RPM thinking surely that was it, but no dice. The MAF is clean, and the wiring all looks solid to me. And Im out of ideas people.

The turbo seems like maybe it leaks, but i dont know jack about forced induction. I assumed it wouldnt be causing misfires all over the place. smoothest place on the tach is 2000 RPM, shakes violently both above and below. Whos got some advice for me? Ill get some photos for yall, hang on..
 

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I had this with my 2007 XC70, same engine, and replacing the coil packs really made a huge difference. I think the detection systems of those years weren't very accurate when it comes to electronics.
 
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