I would like to fix this smoking issue I have with my 94 xjs, 6cyl, 112k. Hopefully it does not entail the engine block. The car smokes when started and then the smoke fades away after about 15 min. It only seems to do this when sitting overnight. I do not notice any change in oil or any antifreeze being lost. The transmission was way overfilled, so I drained it to the appropriate level.

Also, I didnt notice this until I put 10w30 oil with the lucas additive. I then drained the oil and am now running it with 20w 50. It didnt seem to make a difference, but maybe it is the Lucas additve burning off, as someone here suggested. The car gets a driven a few miles every week so maybe the Lucas Ptroleum stuff is still burning.

The car runs fine, seems to have decent power.

I attached photos. The smoke dissipates rather quickly. Head Gasket? Valve Seals? Pistons? (compression test reads 170 on all cylinders except the 6th one which reads 160...). Any Thoughts appreciated.

Within 2 min of starting:



About 8 min after starting


15 min after starting:

 

Might just be water vapor.

Water is a byproduct of combustion and can accumulate in the mufflers....especially if the car is driven short distances. Takes 10 minutes or so for it to get hot enough to burn off.

Leaking valve seals can cause a puff of blue smoke on start-up after sitting over night. It usually disappears within a few moments though.

A leaky head gasket allow coolant to accumulate in the cylinders overnight and give of white vapor on start-up....accompanied by a sweet smell to the exhaust. One good way to verigy a leaky head gasket is to have a repair shop use their exhaut gas analyzer to "sniff" the coolant for hydrocarbons.

Cheers
DD

 

This could be the case. I live in the city, hence the bumper damage in the photos. I may drive it all day on short two mile runs. Though, there is a LOT of smoke coming out. The photo doesnt show how bad it is. I dont see anyone else's cars doing this to the extent mine is.

 

To check the condensation problem, take a long highway run of at least 50 miles. Then park it overnight. See what it is like in the morning. If it is much improved, it is condensation.

Did the drivers in your city all fail the parking by braille method?

BTW, stay away from Lucas additives.

 

It seems like the name Lucas and Auto Products do not fare well together.

I noticed the hose from the smog pump to the air filter housing was not attached. I must have knocked it out when changing the oil. I'm guessing this was my issue. The smoke being bad air fuel mixture when warming up. I cant start the car yet because I am replacing the alternator (it had a bearing noise that was annoying me). I'm hoping there is no smoke after starting her with the pump hose actually attached.

 

I've concluded that it is actually oil burning off. Now the question is whether or not it is the valve seals or the spark plug gasket. I pulled the plugs and the threads were covered in oil. I noticed the spark plug gaskets were heavily leaking oil down to the plugs and seeping through the threads. I imagine this happens when after driving it and it sits while still warm. The more I drive the car, the less it smokes on start. It seems that 12 hours is the time that it starts to get really bad.

I just ordered a cam cover gasket kit. The cam cover gasket was brittle and leaking badly. I'm guessing its never been changed in 110k.

I am contemplating changing the seals since I can only guess that they are in bad shape as well. Rubber seems to last about 20 years... I am going to start with just the cam cover and spark plug seal kit.

Though I live in San Francisco where even a little smoke is unacceptable, with people eating at expensive restaurants out on the sidewalks, etc. I dont want to be that guy who just blows burnging oil at everyone. I'm determined to get this old jag free from oil burning. Even if it means major engine work.