Idle misfire after timing belt

Vavolvos · Post by **Vavolvos** » 15 Sep 2024, 15:36

Hi all, so I’ve got a new to me 2000 Volvo s80 2.9, my last one cracked the block back in 2018. I drove it home and it had a vibration but nothing horrible. I did all my preventative maintenance on it including the timing belt. After the timing belt was done I fired it up and it did fine and I moved it to my backyard. Brought it back up front today and after it ran for 10-15 minutes it started idling funny like it had a misfire and the check engine light came on for O2 sensor codes and 2 cam codes(644A and 6440) I pulled some thing apart to verify timing and my timing marks are good. I also looked at the adaptations to make sure nobody before me played with the VVT and it all looks good to me. I’ve attached my code list and my adaptations to see if you guys can see something I’m not because I’m stumped. I know it had one of the two codes before I did the belt, but don’t remember which one. Could it honestly just be a failed VVT solenoid? If anybody can help I’d appreciate it I’m fighting a losing battle with how little time I have to fight it

pranayama · Post by **pranayama** » 06 Nov 2025, 18:24

Were you able to identify the reason for the misfire if you already did. I am a DIYer myself and lately I have similar symptoms with `Engine Service Required Urgent` message. I am assuming it is in LIMP mode and not sure if they are the ignition coils.

tigerpaw458 · Post by **tigerpaw458** » 06 Nov 2025, 18:35

I haven't done many 2.9s but I'm assuming your working on the non turbo. And I'm assuming these is not your first timing belt on these Volvo's. I know that in some of these early white blocks with single vvt cams, some are spring loaded and you gotta hold the CVT while you aligned the sprocket. You almost need 3 hands to do it. Or might just be the vvt solenoid, 90% of the time with those codes.

dikidera · Post by **dikidera** » 07 Nov 2025, 13:12

With these engines, first you make sure that the markings align on the crankshaft, and then ensure that the camshafts are locked with the tool, finally you align the VVT(old models used a spring). Finally, good tension, allowing no more than 45 degree bend of the timing belt(but at least around there).

More than not most of these issues is VVT, if not then something moved.