Car smoking

Burned valves do not cause smoke. I assume you mean from the tail pipe and not under the hood or dash. Blue smoke is caused by burning engine oil. White smoke is a sign of coolant getting into the combustion chamber, typically from a leaking head gasket. Black smoke means there is too much fuel going into the engine.

The test they probably performed was at the radiator with a glass cylinder partially filled with two chambers of dark blue liquid. That tells if combustion gases are leaking into the cooling system. While that usually does happen at the same time, it is also possible for coolant to go only one way into the engine where it is burned.

Regardless of the results of that test, there are two other things that will identify a head gasket problem. The first is just to observe the coolant level in the reservoir. If it goes down over time and you do not see any external leaks, where did it go? The second thing you can do is to add a small bottle of dye to the coolant. It is dark purple. After driving far enough to see the smoke, you check with a black light. The dye will show up as a bright yellow stain. If you see the tail pipe coated in bright yellow, you have definitive proof the head gasket is leaking.

You need to start a new question. When you piggyback on a previous one, I am the only person who is going to get an automated e-mail directing me back here. No one else is going to see your post or be able to reply. That is doing yourself a disservice.

An EGR valve will not cause smoking from the tail pipe. All that valve does is redirect exhaust gas, which is supposed to be going out the tail pipe anyway, to run back through the engine again, then out the tail pipe. When the valve sticks open, it can cause a rough idle or even stalling, but it is supposed to be open under most driving conditions while at higher speeds where you won't notice it.

There will be some water vapor leaving the tail pipe, maybe even dripping water. That is a byproduct of a properly working catalytic converter. A lot of white smoke is a sign of burning coolant. Blue smoke is engine oil, and black smoke is too much unburned fuel.

Please start a new question. The only people who will see your post are those of us who have posted a reply. None of the other experts will see it or be able to respond. That does you a disservice.

When you post your question, you need to add a lot more detail. There are a lot of things that can cause excessive fuel consumption. We have to have an idea of what is happening or what symptoms you're trying to solve to know where to start. Your question is like telling your doctor you are in pain over the phone. He will have no idea if you have a stomach ache, you cut your foot off with a chainsaw, or your ex-girlfriend came back!

Be sure to list the correct engine size since some have very different fuel and ignition systems.

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Also take a look at these articles:

https://www.2carpros.com/articles/white-smoke-or-steam-coming-from-the-exhaust-pipe

https://www.2carpros.com/articles/head-gasket-blown-test