Smoking Engine Help

Yesterday my XJ started letting me know that the engine's days may be limited. After sitting in a fast food line and pulling out into the road I looked in the mirror and saw a large smoke cloud about the size of a Suburban. I hoped it was someone else but this morning the same thing happened as I left the place where I got breakfast.

Today after work I let it sit in the driveway running for 15 min. Nothing happened until I put it in gear and started to move then it started smoking. I got under the hood looking around and heard nothing but the normal sounds of an engine with 215K on it. I revved it up one time and smoke came from under the intake. The only oil I saw under the hood was a little spray on the firewall behind the intake and a small run from the valve cover. Then smoke was almost gone a few minutes later and completely gone after a short one mile trip.

Any ideas on what is going on. I ran the thing wide open for a few gears with no bad sounds or smoke. Letting it idle for a long time in one place then moving seems to be the key.

I'd say your valve cover is leaking, it's pooling up, and when you move it's dumping that pool of oil on yoru exaust. Fix the valve cover gasket, see what happens.

Sequoia

I thought that I should have explained it better. The smoke is coming from the tail pipe. There was only a puff or two from under the hood. Heck its got several problems that I know are from wear(the main one is lower oil press. than spec) so I guess I should just plan on a rebuild or another engine.

Thanks

Oh, from the pipe...well..that's something different entirely!

What color is the smoke? Is it straight up grey/silver/white, or is it kidna gray but with a bluish tint to it? If it's almost white it's water you're burning, meaning you have a blown head gasket. If it's blue it's oil, which could be a head gasket, rings, or valve guides...Sounds like you've got to at least pull the head soon...

Sequoia

I would call it a gray and there was probably a blue tint. I did jump out and smell of it and didn't notice any antifreeze odor but also didn't smell much burning oil either. I don't have a good nose anyway so I wouldn't trust my sense of smell. The reservoir is full but I didn't check the rad. After thinking it may be a puddle inside that runs down a valve guide.

I sure was hoping that it would make it to 250K.

Its also down on power and fuel mileage but I just installed a roof rack with all the goodies and don't know it that is what is causing the lost power and economy.

Well, I'm quite confident you're burning oil then. Anything bring this on, or just age? You want to do a leak down test of the cylindars and check valve guids, all that. Hopefully the problem is all in your head (no pun intended ) and you can just get that done.

Sequoia

Do a compression test and, if you can borrow the equipment or find a shop to do it, a cylinder leakdown test. That'll tell you a lot.

Your problem could be as simple as needing new valve seals.

GSequoia

Not really,

I changed the oil about 500 miles ago and I've noticed that the pressure seems to be a little lower than it usually is on a new oil change. Dad has a compression tester so I will try that this weekend.

What he said

Sequioa is right on the money. With grey, blue smoke you probably have rings, valves, gasket or combination. Do a compression check and see if it's the valves or rings (rings: pressure increases by squirting oil in the cylinders). You can run a long time on a tired engine, just depends how much power loss you're willing to put up with.

OK, if it starts smoking after idling for a while when its hot, it is shot valve guides, not rings. The fix is a valve job and having the guides sleeved, not knurled. Most rebuilt/crate motors have had the guides knurled. Knurling will last about 20k miles and then start smoking again.

A compression check will not show valve guides. The reason it smokes after sitting idling is that at an idle the vacuum is the highest and it sucks oil down the intake guides. If you leave it idle, it will look like you are spraying for mosquitos.

While it is a hassle, it isn't the end of the world. It takes a couple of hours to get the head off if you know what you are doing. The valve job will run you $150-200 with guides. The head gasket/valve seals/intake gasket/valve cover gasket will run you approximately $40-$50.

Some people try and get away with just replacing the valve seals without pulling the head. This may work for 10k miles or so but is not a long term fix.

I have been overhauling engines for 40 years and you can trust me that it is the guides if it smokes after idling for a few minutes when hot. You probably don't even use much oil between changes. In Colorado, it will fail the emissions test because they idle for several minutes, turn the vehicle off, then when they restart, if it has a puff of oil, it fails. This test is specifically looking for valve guides.

old_man

Thanks for the help. I agree with you on the oil going down a valve stem. Just to be clear it seems to only smoke when moving after it idles for a long time. I let it idle for 20 min. today with no smoke until I started moving. I did a compression check today and got

1 130
2 140
3 140
4 150
5 140
6 145 I think the problem is on this cylinder, the plug was a little darker than the rest.

I haven't checked for the spec yet so I don't know how low I am. The thing needs the pan pulled off for a rear main and to check the oil pump strainer anyway so I may break down and pull the head if the pressures are close to spec instead of doing a complete rebuild. Since it needs done anyway it won't be money wasted if I have to rebuild it soon.

Thanks

Sounds like your compression is fine. If the guides aren't too shot, the smoking doesn't happen much until you bring it off of an idle. The oil builds up in the intake but doesn't get pulled into the cylinder until the flow increases.

Tom Houston

Good Advice

Tom has given you geat advice and I can vouch for him as I am running one of his rebuilt engines and the only oil leak is the gosh darn AMC valve cover (soon to be resealed).