My truck puffs blue smoke, but only after I sit at a stop light for a minute or so and the engine is at operating temperature. When I press the gas that's when it smokes, but eventually stops. If I get on it hard it seems to blow out instantly and clear up. If I'm stuck in traffic it will even smoke at idle and then really puff when I accelerate, but it clears up under a load.

Does this sound like a valve seal problem? Anything else I should check while I'm in there?

 

sounds like valve stem seals to me.

 

x2... that is indicating that the oil is getting past the valve seals. you can yank the plugs and see if you can determine which cylinder has the problem and look into getting it fixed. there are ways of swapping valve springs & seals w/o having to yank the head.

 

My Grandmother had that issue, it was the seals. However, instead of tearing the motor apart.. I changed the oil with the same oil, minus a quart. Use Marvel Mystery Oil for the last quart and it cleaned up the issue.

Hope this helps.

 

Thanks for the input guys. I figured those were the culprits but I wanted to make sure. My truck is pushing 180,000 miles but has been VERY well taken care of, drives like new, and has no issues other than this, so you could imagine I'm pretty concerned about fixing it.

I was running some of those NKG Iridium plugs in my 4.7 and it, quite literally, melted one of my ignition coils. As far as I know it was gapped at the standard .040, so... maybe that had something to do with the seal failure (either carbon deposits or heat damage).

Thanks for the mystery oil suggestion, I will try that first.