Misfire at idle

[mechman458]

Hey guys. Got a rather tricky one here. I have a friend with a 2004 Vectra C with a Z32SE. Oh yea should say I'm I'm Australia. Ok so he's asked me to have a look at it as it has developed a misfire only at idle. If you bring the rpm up even 500rpm it's sweet. Drop it to idle misfire. DTC list shows misfire codes p0301,p0303,p0305. Which is misfire on cylinders 1,3,5. I've checked all vacuum lines, manifold, spark plugs, coil and cam timing but so far I've found nothing. Like i said you can drive this car no worries part throttle wide open and she drives mint. The moment it's at idle game over. Any help here would be fantastic.

Thanks

Luke

[Ben50n]

Misfires are normally electrical, so check the usual suspects, coil, plugs, leads etc. You said it misfires on 1,3,5 which is one side of the engine, does it have 2 coils i.e. one per bank or a coil to each plug?

Is there two different sensors to tell it when to fire? One for cylinders 1,3,5 and the other for 2,4 and 6?

[mechman458]

Yea 1,3,5 is the rear bank, closest to the firewall. It has 2 coil over plug setups one for 1,3,5 and another for 2,4,6. As far as im aware the crank angle sensor together with the cam angle sensor tells the ECU when and what to fire