Denali 6.0L P0300 Random Misfire

[whatnot]

My dad had an '02 GMC Sierra Denali with 6.0 liter that has been getting a random misfire code. Sometimes it flashes the SES light while driving.
So far the fuel and air filters and spark plugs were changed and the MAF was cleaned.
Is there a common cause for this or is it going to be a lot of parts replacing?
Also, it sounds like it might have a small exhaust leak. Can that possibly cause the misfire?

 

[ockgator]

hook up a scanner and look at misfires, should show current and history misfire... you want to look at the history #'s

 

[oldbrownsierra]

Check all plug wires. After being replaced, or replacing plugs, they tend to pop off for the first while. Mine did for about 6 months, and has been fine since.

 

[Ed HD]

I'd replace the wires. They're relatively cheap, and one more variable eliminated. Be sure you use di-electric grease on the boots. I like the Beldin Premium wires from NAPA.

 

[whatnot]

He took it to the dealer and they said it is the injectors. They cleaned them and said there were a couple that were still misfiring. They told told him to drive it for a while and if they don't clear up then they will have to be replaced. It has been quite a while since then so he will have to get them replaced.