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White smoke from exhaust - could it be anything other than head gasket?

My teenage son drives a 2000 Mazda 626, close to 200K miles, auto, 4 cyl. About a week ago, it started occasionally emitting a burst of very thick white/gray smoke on start-up. The smoke smells like fuel and lasts just a few seconds. Doesn’t happen every start – maybe once out of every five or six starts – and not necessarily first start-up of the day. Car runs fine and has not overheated. Is there any hope that it could be anything other than the head gasket? I’m asking here because our Mazda mechanic can’t even look at it until the end of the week and already told me that if it’s a head gasket it isn’t worth fixing on this car.

If the head gasket were leaking coolant the smoke would smell like anti-freeze, not fuel. Are you losing coolant?

It could be oil leaking past the valve guide seals, or injectors sending too much fuel into the cylinders at start-up, or both. At 200K miles the possibilities are many.

Don’t assume the worst. Have the engine tested for a leaking head gasket before you start making plans. The gasket may be fine.

Not losing coolant, and it definitely doesn’t smell like anti-freeze. Thanks for answering and giving me a little hope!

If it’s gray and smells like fuel…then it sounds like it’s just running rich…

Could be fuel injector…or not tuned properly (when was the last time the plugs were changed???)

It’s probably an injector that’s leaking down when the engine is off. I would still get the engine tested.

This car is old enough to have a leaky fuel injector.

I would leave it alone until when/if it gets bad enough to last longer, affect idle or cause the check engine light to come on.

The white smoke is unburned gasoline. This can be caused from a leaking fuel pressure regulator. Locate the fuel pressure regulator and remove it’s vacuum hose. If gasoline leaks from this hose the regulator is leaking and requires replacement.


My previous car before the 2002 Sienna was a Dodge Caravan. At one point, it started having problems, I forget what they were. I took it to a radiator shop to have the radiator serviced. The mechanic told me to shut it off, and when it was cool enough to be safe, took off the radiator cap. When I started it, the coolant very quickly developed bubbles and foam. He said that was guaranteed to be the head gasket and compression was pumping into the cooling system. I thought I’d pass this on, you can be sure if this is bad information the good mechanics here will object.