I'm having an odd smoking issue with my XJ.

It doesn't smoke at startup, it doesn't smoke under hard accelleration, it doesn't smoke driving down the road...

It does, however, smoke whenever I'm in a drive-thru or stuck for a long period at a stop light or in traffic. Smoke just starts rolling out. Since it's doing it in traffic I haven't gotten out to see what color it is from a different angle, but it looks to be blue/white and smells pretty bad. I know blueish implies oil, but I don't seem to be using that much, and to be honest I'm only really noticing the smoke after the electric radiator fan kicks on (man, the entire Jeep vibrates when it comes on, I think I need to replace it).

On a whim, the last time it did it, I put it in neutral and revved the engine to see if I could blow it out. Nope, didn't make any real difference. Once we started moving again, and got to the next light, it wasn't doing it anymore. I don't seem to be loosing coolant, although this morning I added about half a quart of water (had it flushed on Saturday, so I suspect they didn't totally fill it).



I'm at a loss as to where it's coming from. Normally I'd just chalk it up to something like worn piston rings or leaking valve seals, but I'd expect it to blow smoke all the time. Not just when it's hot and been sitting a few minutes. I'm starting to suspect that what I'm seeing isn't coming from the engine, but is instead coming from the catalytic convertor, especially if it's getting really hot, causing it to burn off whatever is in it.

I've also picked up a rattle coming from somewhere on the front of the engine. I think it's one of the accessories, though, and not a main bearing (those typically let out a horrible squealling noise, don't they?). Probably the power steering pump.

 

My money is on faulty valve guide seals, I have a 90 Caravan with a 3.0 V6 that looked like it was on fire when sitting idling. It never smoked at Highway speed. I had it overhauled at 132,000 miles which fixed the problem but I would have driven it anywhere before the rebuild. It was more annoying and embarassing than anything.

 

my 5.2 dakota does this. it is my valve seals. it's now off the road till i fix it.
does yours smell at idle?

 

Not really, most of the time it doesn't smoke at all at idle, just when it's running warm.

I was always under the impression that valve seals would cause oil to leak into the cylinders when parked, and it would smoke pretty bad at startup? That's why I'd almost discounted them, since I don't have any smoke at startup.

 

Code, smoke like you describe is a bit more difficult to diagnose the source of. You can do a compression leak down test to see if it is rings or a bad valve seal. But either way you are still gonna have to spend some bux to fix it.

 

Figured as much. I'm probably just going to let it be. It seems to be running fine.

 

Smoke rolling out of where? My XJ will start to leak from the rear main if I get stuck in traffic for a while and it's above 50* or so outside.

 

I have the complete opposite. I have smoke pouring out at speeds of 60mph or more. I have changed the oil pan gasket and the oil filter bracket and seals ...Tj

 

The smoke comes out of the back, I'm guessing the tailpipe.

I have NO SMOKE at highway speeds up to 80mph, I did a sustained jaunt at that speed to Orlando over the weekend with absolutely no issues whatsoever.

 

For me there is no smoke coming from the motor (thank goodness) its definitely oil but I cant pin it down and it only does it over 60mph..strange huh...Tj

 

Bunk valve guides are the culprit!! Oil will collect on top of them at idle, but at speed it's flowing faster, so no smoke. I don't think it's a major deal to R/R them. You will have to pressurize each cylinder as you work on the valve, so it doesn't fall into the cylinder. If that happens, it just turned into major surgery!! HTH!! Laters!!

 

Any ideas on my problem...Tj

 

How many miles do you have?? Yours sounds like the rings are shot, but I'm not sure about that. When you drive faster your engine developes more crank case pressure and it will blow oil by the rings into the combustion chamber, does that sound like what you're experiencing??

 

Yours sounds more like blowby to me, Jim. Maybe check the vent line running from the backside of the valve cover to the intake? Mine was totally clogged solid.

At this point I'm not sure if it's worth fixing, I don't have a lot of spare cash laying around to sink into the Jeep. As long as I don't sit around idling a lot it's fine... usually doesn't start smoking until it hits the 5 minute mark. Most stoplights it's fine, it's usually just showing up at rail crossings and the two times I've gone to Burger King on the way home from work.

 

My friends 94 does it, and it still runs great!! If you can live with it, then don't bother.