my 1996 volvo 960 has a very rough idle. my scanner reads p0306 code which means misfire emission level cyl 6. trying to troubleshoot this but it can be so many things. from spark plugs, ign coil, exh gasket, injector, exh valve to catalyst converter. already change spark lugs during regular maintenance and switched ign coil from cyl 6 to cyl 1 and re-scan. still reads p0306. i can hear air coming out from near cyl 6 but can't pinpoint from where. any help will be greatly appreciated. volvo mechnics are hard to come by in these parts and the dealer will kill me financially. thanks

have you tried spraying wd40 on the intake manifold to see if it will smooth out the idle. The intake manifold is known to go bad on these cars.

My money is on that gasket, if its never been replaced i think thats it.

good luck

I will bet that you have a burn't valve.

Try doing a compression test.