Hello, first time poster here...
My wife drives a 2002 I35 that hasn't given us any real trouble over the years. She is the original owner and the car has about 130,000 miles on it. Recently, she has noticed a puff of white smoke when the car is started. It only happens after the car has been in the garage overnight or parked for several hours at work.
We took it in for an oil change recently and asked the shop to check it out. They were unable to find anything.
We would appreciate your thoughts on what might be going on and how to remedy.
Thanks,
Judy & John

 

White smoke could be several things. A puff of smoke only in the morning would mean this is in the early stages.

It could be water which would mean a head gasket. A cooling system pressure/leakdown test should show this.

It could be oil burning. Normally oil creates blue smoke but a small amount could look white. A compression check would show worn cylinder rings.

A cracked/broken compression ring on a piston. This problem would cause a puff of smoke smoke when you start the engine or accelerate after sitting at idle for a bit. Plus it would be constant all the time the engine is running.

Too much gas in the cylinder when you start. Normally too much fuel creates black smoke, but again, a small amount could look white. Usually looking at the spark plugs would show this, the spark plug being a black color. In you case, it may not be bad enough to cause discoloration.

In all cases, the smoke should have an odor. Anitifreeze in the water would smell kind of sweet. Oil has a distinctive odor that I don't know how to describe. Gasoline smoke smells like gasoline.

This might be a case where the problem will have to get worse before the problem can be found.

 

Diagnosis was fuel injectors. We had them cleaned with some serious chemical along with the intake ports and valves. 98% of the smoke is gone on cold starts. We're hopeful the little bit of smoke still occurring will go away in the coming days.