2000 S40 T4 ph2 occasional misfire.

[V40DSchariot]

Thought I'd throw this one out there, see what comes back.

My S40 T4 has started having a serious misfire, but only occasionally. This year it's had new coil packs (pattern part), new spark plugs (genuine). Fault code of P0302 cylinder 2 misfire.

I've swapped the coil packs over and swapped with the old ones (still the same), swapped the spark plugs over and swapped with the old ones (also still the same). I did find a spark plug with the electrode gone, possibly burnt away, but that was on cylinder 3.

The plugs going to the coil packs have become a little dodgy on one of the cables so crimped a new connector on that cable.

And it's intermittent, round town can be fine or kangaroo juice, 70mph can be fine or serious misfire creating serious vibration and little acceleration.

The only thing I've not checked is the LV wiring to coil packs.

I do have an issue with the osf headlight, which after checking I assume is to do with the wiring loom under radiator issue, but surely that wiring loom wouldn't affect the coil packs...would it?

Thanks in advance as always.

[clarkey1984]

As a fault finder, and also a pretty cheap thing to change, I'd stick a new fuel filter on, even if it makes little difference to the misfire you'll have a little more poke when it is running smoothly.

[Baffler]

Also consider that a tired/lazy fuel pump (service life of ~100k miles on a T4) will cause the engine to stutter under load, just like a dodgy coil pack, especially noticeable when below 1/4 on the fuel gauge as there isn't enough fuel to keep the pump cooled.

[kmb]

My 850 T5 had this, only on occasion and under a light throttle in a high gear- very difficult to trace but I solved it with new Bosch HT Leads.

Might be worth a try if not yet covered.

[V40DSchariot]

Found the receipt for the spark plugs and got in touch with the Volvo garage where I got them, only brought in August , so got a replacement set. Never seen a spark plug like it.
So either after finishing my nights or if it stays dry long enough to swap them over, see if that sorts the issue.

[clarkey1984]

Christ, for that to end up like that something else must be going on in that cylinder surely, as plugs don't just go like that, it looks like it's been fished out of the bottom of a well

[V40DSchariot]

Yeah couldn't believe the state of it when I got it out. The porcelain top was loose so makes me wonder if they'd been dropped at some point.

New plugs fitted and it's definitely better, but on driving it has missed a couple of times. Coming up with fault code of coil pack.
Tried the old coil pack so back to the new one, see if that improves things.