I would check them all. It could be simple as one plug of the 16, but you will have to find it. Sometimes if you advance your timing with a tuner etc. you might have to run a colder plug to prevent pre-ignition. For now I would check all of the gaps and see if that is the culperate.

 

I would check them all. It only takes one to mess up a cylinder.

 

What is actually causing the vibration? is it not firing correctly? so i'd be losing hp correct?

 

Well, it could be any number of things. What you are describing sounds like irregular engine idle. It is usually due to spark plugs that are incorrectly gapped. If so, the spark plugs can upset the air to fuel mixture, which in turn affects combutsion and idle. But yes, you can get hesitation, knocking, missing etc.

 

when i did plugs, the stock replacement champion coppers from napa came pre-gapped.....that meant that only 4 of them needed adjustment instead of all of em i guess lol. Take your time, take em all out and now you know for next time...I hate doing stuff twice, but its the only way to know for sure.

 

Yeah I agree with redoing them all. It's a PITA I know but thats the only way you will know for sure.

 

Yep, pull 'em and gap 'em. I've found that a good 40% of "pre-gapped" plugs are off. It doesn't take much for a misfire. Misfires are a definite cause of an unsteady idle...

 

MY motor has 75k on it and I'm dreading changing the plugs. At least I only have 8 lol

 

I'd love to be you right now lol when i take these all out and gap them it'll only be like doing 32 plugs

 

I wasn't going to say that lol, as he is in enough pain already. Big, I understand completely man.