Misfire?

reigox · Post by **reigox** » 23 Sep 2024, 03:05

the problem started after a 100km drive. While idling the engine is jerking/jumping after every 5 seconds or so.
When i give it like 70%-100% gas, then the car starts vibrating or jerking/jumping

reigox · Post by **reigox** » 23 Sep 2024, 03:06

engine is 2.5T, automatic gearbox

dikidera · Post by **dikidera** » 23 Sep 2024, 03:49

I would first inspect the coil packs and then spark plugs. Usually the first culprit.

Post by **vtl** » 23 Sep 2024, 06:21

To me it sounds like one of exhaust valves are not sealing properly, it will burn soon. I had this sporadic chugging for a few months, then it finally burned. This when it quit:

It commonly happens around 220-250k miles (350-400k km over the Pond), thanks Volvo for switching hydraulic lifters to solid tappets.

You would need to rebuild the head. Perhaps, replace the piston rings, because it is so easy with the head off.

reigox · Post by **reigox** » 23 Sep 2024, 06:30

I forgot to mention, the car has a code aswell ''Catalyst System Efficiency Below Threshold (Bank 1)
Does that have something to do with the problem?

Post by **vtl** » 23 Sep 2024, 06:35

reigox wrote: ↑23 Sep 2024, 06:30 I forgot to mention, the car has a code aswell ''Catalyst System Efficiency Below Threshold (Bank 1)
Does that have something to do with the problem?

Yes. There's unburnt fuel in exhaust that overruns catalyst's working capacity.

reigox · Post by **reigox** » 23 Sep 2024, 06:37

vtl wrote: ↑23 Sep 2024, 06:35
reigox wrote: ↑23 Sep 2024, 06:30 I forgot to mention, the car has a code aswell ''Catalyst System Efficiency Below Threshold (Bank 1)
Does that have something to do with the problem?
Yes. There's unburnt fuel in exhaust that overruns catalyst's working capacity.

Can i drive it like this, and for how long?

Post by **vtl** » 23 Sep 2024, 06:47

reigox wrote: ↑23 Sep 2024, 06:37 Can i drive it like this, and for how long?

You can drive it like that until fixed. The longer you drive, the longer and more expensive fix would be

Post by **jonesg** » 23 Sep 2024, 12:22

vtl wrote: ↑23 Sep 2024, 06:21

It commonly happens around 220-250k miles (350-400k km over the Pond), thanks Volvo for switching hydraulic lifters to solid tappets.

You would need to rebuild the head. Perhaps, replace the piston rings, because it is so easy with the head off.

its commonly starting in mine but we hardly drive anywhere these days.
I've seen rebuilt heads for $800 online.
I think I'll do a compression test before dropping $1000+.

Post by **Krons** » 23 Sep 2024, 13:37

reigox wrote: ↑23 Sep 2024, 06:30 I forgot to mention, the car has a code aswell ''Catalyst System Efficiency Below Threshold (Bank 1)
Does that have something to do with the problem?

Any coil codes?