the misfire is very random.i had a vectra 2.5 and the dis went on that.the guy said it could be dispack breaking down giving misfire on 4 but as weve had some damp weather i was going to dry the connectors on the ecu tomorrow.funny thing is,i pulled into my drive with it misfiring, turned it off and restarted it and the misfire had gone. if i was going to change spark-plugs, what ones do i get?are 2.5 the same as 3.2?
My 2.6 started doing EXACTLY the same thing last week -reporting Random misfire & misfire cylinder 4 (codes shown are 0300 & 0304). Occasionally got the cat light flashing, but just like you, would stop, restart, and everything back to normal. I did post a thread here, and the general consensus was the coil pack. My car is under warranty, but there is a high excess - I've ordered a coil pack for the 2-4-6 bank, and it should come in the next few days, so I'm gonna swap it. Could be oil, but I only had new plugs 3k ago, and the wells were bone dry.
It also happens much less the colder it is! -8.5 at 0600 today, started like a summers day, and did not miss a beat. A few misses on the way home tonight, but no light.
Strange that mine is on Cyl.4 too !!!
