P0306 Misfire CYL 6

[JW]

i did a search and what the previous post said was a vacuum leak, im wondering if mine is the same.
'98 3800 non/SC in a bonnie
mine only has 70k, and this is the only code i get. it only does it when its warming up. i replaced the plugs and wires.
could it be the ign module itself?
one other wierd thing that i dont think is related, i got a coolant leak that i cant find(going to the shop fri for that)I hope its not a head gasket.

[Justin]

Hmm, the problems might be related, how did the plug look when you removed it? Maybe coolant leaks into cyl. 6 until it warms up, then the leak seals. Don't go condemning the head gasket or intake right now, I'm just saying the probs might be tied together. Does the exhaust smell sweet when cold?

[GPRACER]

the 3800 has a known issue of leaking coolant at the throttle body to upper intake mating area. Usually just replacing and retorqing the three throttle body nuts fixex this. IF it's the problem.

PO306 may not be ignition related, could also be injector/fuel related.

[JW]

thanks for your replies.

i had to go away for work so my wife took it to the shop. they had to replace the intake manifold. there was a coolant passage or valve broken inside. i would like to shoot the engineer who thought a plastic manifold would be a good idea. the tech at the shop said the aftermarket manifold that he put on there should hold up better than OEM.

on a lighter note my monte got 32mpg at an average of 69mph on this trip.(thats including stops for gas and lunch)