How do i clean cmbustion chamber.i understand this will cure cold starting problem

White smoke normally indicates an internal coolant leak from a bad head gasket or a cracked cylinder head. A healthy engine will have some steam/vapour from the exhaust when starting from cold but dissipates quickly. If your exhaust smells 'sweet' it will more than likely be coolant making it's way into the combustion chambers. Check your spark plugs. Coolant entering a combustion chamber clears carbon deposits so if one or more of the plugs look suspiciously clean, it will indicate the probable location.

there is no effective way of cleaning a combustion chamber other than to remove the head and use wire brush or scraper. In reality after the use of leaded fuel was stopped the modern cars only carbon up or soot up and seldom need decarbonizing
I suspect that you have a detonation problem (pinging sound on acceleration). run the fault codes first before you do anything drastic.

I'm not a professional mechanic but the fuel pump does that and it has to have a clean fuel filter to do it effectively.

Replace the chock thermostat. When the engine is cold, the choke is in closed position to restrict airflow and give rich fuel mixture to combustion chamber. As engine area warms up, the choke thermostat gradually opens air passage to increase air flow to combustion chamber, resulting in leaner fuel mixture. The choke is in "full open" while the engine is cold, resulting in lean mixture, causing the engine to die unless you add more throttle to increase fuel mixture.

is there any codes in the vehicle? possible the spark plugs have some build up and not getting sufficient heat or ignition coil also gets build up and not fire enough to burn the fuel in combustion chamber.i would check those probable causes and have it scan if needed.

First of all I would investigate further. How did they determine bad cylinder? I've seen that cured with a simple can of combustion chamber cleaner run through it. Let me ask. Does vehicle get lots of highway driving ? ( that helps keep combustion chamber clean ) If you can provide me with a few more details such as driving habits, mileage on engine, what engine you have, how often it gets service and tune-ups etc, I can help you dig a little deeper before writing that engine off. My guess is it's simpler than what you were told but lets check a few things just to be sure.

An engine will burn oil for several reasons, mostly related to wear. First, the rings on the pistons can wear, allowing oil to get past them into the combustion chamber where it gets burned along with the fuel. Cylinder bores also can wear giving the same net result. Cure is to rebuild the engine.
Your valve guide seals can harden up and allow oil to pass into the chamber or, the guides themselves can wear essentially doing the same thing. This is cheaper to repair than an entire engine rebuild but still quite expensive if done correctly.
A third way to burn oil is often missed. that is worn engine bearings....when the bearings wear, there is more oil being thrown onto the cylinder walls than the oil control rings can handle...that causes the rings to accumulate carbon deposits that cause the rings to get stuck and then pass even more oil into the chamber.That too is an expensive rebuild to do correctly.
If your engine is leaking at all, you need to consider repairing any of those leaks, providing that you aren't using huge quantities of oil and not smoking from the exhaust to any great degree. That will cut your usage down somewhat.Also make sure that any venting system is working properly (pcv etc) pressure buildup in the crankcase can force oil to go where it does not belong, externally and internally.
First thing you need to do is to monitor just how much oil you are really using. If you are using a quart or less in 3,000 miles, you might want to consider using a good synthetic oil and a good additive like lucas engine treatment. That combination will help clear carbon from the rings and soften and restore valve seals.
If you are using far more than that, there is no chemical that will put metal from worn parts back on them. Only cure is a total rebuild or engine replacement. Only you can decide if the car is worth going through that expense to repair.
Hope this helps you understand it better!
Good luck and ask if you don't understand any part of what I said!!!

Idler air control is going out and clean throttle plate

If your engine is feul injected then it sounds as if the cold start sensor is faulty. It acts like a choke in normal aspirated engines, by allowing more feul into combustion chambers to allow qiucker starting. Suggest check all wiring plugs on the fuel system. Apply suitable cleaning solution to plugs if possible.

Have replaced your glow plugs?They dont cost alot to replace,try this