2008 S60 2.5T, Misfires on cylinders 1 and 3

Post by **jonesg** » 23 May 2025, 06:31

coil is failing under load, swap #3 around and see if the fault follows the coil.

Vova585 · Post by **Vova585** » 23 May 2025, 09:16

Any chance this car was in the hands of "crafty teenager" that was trying to tune it? K&N filters, straight pipes, etc? I am scratching my head what can possibly be wrong.
Another not very expensive option is to buy a harness for ignition coils.
https://ebay.us/m/gg55uO
Vs replacing connectors for 1 and 3 ignition coils. Possibly the cracked insulation is causing short to power or short to ground. If that's not helping- advance level diagnostic with scope is you best bet.

XC70Rider · Post by **XC70Rider** » 23 May 2025, 21:45

I replaced the IGN coil harness 3 years ago. The heat under that valve cover caused the pigtail connectors and wire loom to get fragile. I had all the pigtails zip tied to the IGN coils before I replaced the harness. Instead of risk it with a new aftermarket harness I got a used harness from ERIE Volvo. No issues since installing it.

With the coils over 15 years old I threw on 5 new Volvo IGN coils I got at FCPEURO. Also traded in the 5 Volvo lifetime warrantied spark plugs.

I've kept the valve cover off since then so the heat can escape.

Check page 4 of the wiring diagram I attached.

Post by **DavidE7** » 25 May 2025, 20:44

If the simple solutions aren't finding the problem there are some more complex things to check.

My S60 had misfire codes for cylinder 1 and 3 after the PCV check valve lost its guts into cylinder 3. See the post below for the diagnostic details. Compression test will provide clues. A bohr scope view inside each cylinder will let you see any mechanical damage from something foreign getting into cylinders 1 and 3 and also allow you to rule out a leaking head gasket with coolant inside the cylinder.
viewtopic.php?t=86687&hilit=Banjo&start=30
Good luck!

professorsunshine · Post by **professorsunshine** » 29 May 2025, 12:50

Bad news. I did some more testing today with different tools. I may have gotten my numbers mixed up or something, but cylinder 3 indeed has no compression. 0, zilch. That explains most of the issues I was facing.

So now I'm moving forward with replacing the cylinder head. Can anyone tell me what cylinder heads are compatible with the 2.5T engine with VVT on both cams?