MISFIRE - help, please!

[HoustonHelix]

Scanner indicates a "Misfire on Cyl #6".

I tried to isolate the problem by switching with Cyl#5 the sparkplug, then sparkplug wire, then injector. Each time I would do a switch, I would reset the Engine Service light, wait for it to come on then do a reading. Each time the light would come on it would indicate the same message not showing it the problem jumping to Cyl #5.

Since I have determined that the plug, wire, and injector is good in Cyl #6, yet continue to get a misfire, could someone advice on what I else I need to check? I read somewhere that there might be a "vacuum leak". How exactly is that checked?

[mikecee48]

It's possible that the intake manifold gasket is leaking at the misfiring cylinder where the manifold bolts to that particular cylinder. With the engine running, spray that area with WD40 and listen for a suction hiss or notice if the engine runs erratically when the spray hits it. You can also use an oil can to douse that same area with oil that is thicker as it may hiss louder when it gets sucked in. If you find a leak, and can stuff some thick gasket sealer into it, and let it harden, you might be able to plug the leak without having to remove/reinstall the intake manifold to replace the entire gasket.

Also, check the intake air ducting for cracks or loose clamps allowing outside air in which leans the mixture. I've seen this happen with the result being that only one cylinder misfires due to the lean mixture.