Hey guys. have an 04 5.4 with about 142k on the clock. In the past few months it has began to develop a vibration at idle that you can feel in the seat and the floor, and I rest my knee on my door panel when I drive and I can feel that too. Its not a miss or anything like that i don't believe because the tach is smooth and consistent and the vibration goes away as soon as the truck goes away from idle. I can literally see my passenger seat and mirrors vibrating at idle and it is incredibly irritating.

Someone told me it can be an issue with the cats? I guess the 04s have 4 cats???

Anyone have any advice?

 

Yes, the 04 has 4 cats but I would check your fan blade. It may not be your problem but I was missing a small part of one blade and my truck vibrated like crazy at idle. My hood would shake if opened and it drove me nuts. I replaced the fan and no more vibration. I would check for codes though. You could have something else going on

 

I had the same problem after I changed my plugs. I didn't have a CEL or any codes but something was definitely wrong. Like you, I could see the interior and all mirrors shaking.

At the time I went ahead and changed all of the boots and springs on the COPs and that made it go away. If you haven't done yours recently it's worth a shot since they're cheap. Even if it doesn't fix the problem it's good preventive maintenance job.

 

I have a set of new COPs so I may throw them in and see what happens. My truck has had a history of the "45 mph misfire" common with COPs.

 

Yeah I'd start with putting those on. Keep us updated

 

definitely check for codes first even if your cel isn't on. I would also look at vacuum leaks before I spent money on it. All you need for that is a can of ether (starting fluid). Just spray it all over and around your vacuum hoses while your truck is running and listen for a change in idle speed.