I've noticed lately that my jeep will constantly puff blue smoke at idle. I dont see blue smoke on start up, and I dont really notice it while driving. But while its idleling it smokes constant.

Is it time for a new engine soon? or whats the most likely cause?

 

Woah, new engine? Basics first lol. When was your last tune up? Do you know the maintenance history? (At least recent) Regular oil changes with a quality filter?

Any oil on your air filter? A common cause of burning oil is a clogged crankcase ventilation system. I couldn't easily find a writeup on how to check and clean the CCV system, but it's there to let the engine breathe. When one of the small hoses running off the top of your engine gets plugged, you can burn oil. Check out this link for pics and details of the CCV system itself: http://www.jeepforum.com/forum/f310/...ite-up-733669/

Cleaning out the hoses and elbows with some TB cleaner should help

 

It could be the valve stem seals or rings.

 

It could also be worn rings or scratched cylinder walls, or both.

 

How much oil are you using? Start tracking it.

A basic compression test (dry, then wet if you have any cylinders testing low) is always a good starting spot here and a good "snapshot in time" of the internal condition of the engine

And yes, as a matter of course, ensure that the CCV system is working properly.

 

Sounds like the typical valve seal issue. Do a compression test to verify. My wife's XJ with a 175,000 mile junkyard engine did this. I spent an afternoon and put valve seals in without removing the head. Doesn't burn a drop now.

 

1 cylinder is down 30 psi from the rest

 

A bad seal for that cylinder then.

 

How did you do your compression test? Dry, then wet? Throttle wide open?
What were the actual numbers for all 6?

 

One characteristic of bad valve stem seals/guides, is when you park it hot, then start it after some time and it puffs blue smoke. Oil ran down the valve and ended up in the cylinder.

One thing with rings. If you decelerate/"backlash", (use the engine as a brake going down hill), that can really load the cyl's with oil sucked past the rings on a good hill. Then when you gas it to take off it blows a big cloud.

If that 30 Lb. number is about right, and that smoke is actually bluish, and not white steam, your plug in #1 has GOT to be ugly, black. I can't say I've ever heard of anyone freeing up one single gummed up ring with Baryman's Chemtool. A nutty thought I suppose.....wouldn't want to further ruin the block running it with NO oil there.

When you get into your engine to look at what's up, sometimes it's not quite what you expect. Tough at that point to do a complete wet/dry compression test to maybe help to figure it out! Also there's the head. Myself, if the wet test provided good steady high numbers for the other five, I might just bolt it back on/run it. Or just "hand lap" the valves (with a drill), and install new seals.

Last month I had low compression on a cylinder of a generator. I had air and the compression tester there so I just hooked the air to the tester hose. I could clearly hear it hissing out the exhaust. Nothing fancy, just took a minute. I freed up the stuck valve.

Sorry Btw. 265K here. My day is coming.

 

I never see blue smoke on start up. The only time I really notice it is at idle when the engine is hot, then it will puff constant blue

 

Probably just valve seals.

 

All that rambling and I read it wrong. ^. Thought you said down TO 30 Lbs, not down 30 lbs.

A neat trick if you want to change seals, feed a length of small nylon cord into to cylinder, bring the piston up by hand and it holds the valves up for you.

Couldn't begin to guess why the low cylinder. I don't see a valve stem seal doing that. Wet/dry compression numbers would help, as said.

 

"Couldn't begin to guess why the low cylinder. I don't see a valve stem seal doing that. Wet/dry compression numbers would help, as said."

That's why I said rings earlier.

 

If you have one cylinder 30# lower than the others and no smoke on start-up, I suspect you primarily have a ring problem, not a valve seal problem. Not that the seals couldn't be contributing to overall oil consumption. They have no effect on your compression though, they are merely for oil control. The valves and rings seal the cylinder.

As others mentioned, re-do the compression test, once with dry cylinders and again with two teaspoons of oil dumped in the plug hole. If the difference between cylinders vanishes with oil in the hole, it's ring time. If the pressure differential remains when wet the problem is more likely valve-related.
Post the actual wet/dry numbers.

Incidentally, the best way to check compression is to crank until the compression stops increasing, then record the final compression number and the number of strokes required to get there. Hitting the "right number" doesn't mean the cylinder is OK if it takes excessive cranking to get there.