I have a problem with one of the spark plugs. It gets dirty and after some time stops working. That causes my car to shake and go 30-50 mph, with check engine blinking. After I (or mechanic) clean the plug everything gets back to normal for some time (a week or two). Then it happens again.

I also blow white smoke from exhaust sometimes (usually when starting a car, but not every time. Problems started few months ago when i filled my audi with some bad fuel (dirty or with water) and it stopped shortly after gas station. After 2 hours of trying, I managed to start a car, but with "explosion" of that white smoke from exhaust. Since then i have problems.

What do you think?

 

If the plug gets fouled with sticky black stuff, it is probably getting fouled by oil.
If it is back & fluffy it is probably getting too much fuel.
Depending on the engine the white smoke could mean different things. Normally aspirated it indicates coolant getting into the combustion chamber. Turbocharged the smoke could indicate a failing turbo, and/or coolant getting into the combustion chamber. May want to do a compression test to compare the cylinder foulig plugs with the good ones.

 

i have a picture of that spark plug. I'll try to post it. It's black but not sticky...

 

That plug looks gas fouled. Being that this is the only cylinder with the problem, make sure the wire and/or coil firing that plug is up to spec. Otherwise the injector may be leaking or stuck open, requiring a cleaning or replacement. However, before changing things make sure the compression in that cylinder is up to spec.

 

Alright. I'll check the compression first, then clean injectors ...

 

you said your cell was flashing. i would first take my car to autozone or advance and have them scan the car. It would be eaiser then just guessing what it is. For a flashing cell though its mostly due to coilpacks taking a dump on you. As for the pillow of white i would say your leaking coolant into the head. Might have a check at your headgasket and valve cover gasket.

 

No I didnt say that cell is flashing. I'm going to check comression on saturday and perhaps clean injectors...

 

It looks like ur cell is flashing according to your first post. You said check engine light blinking right. Cuz thats what im referring too. Either way you probably have a headgasket leak. . .

 

thats not even the right plug............. Your supposed to have single prong. These "performance" plugs have no real advantage unless your into professional racing and tuning.

The engine is designed to run best with what it comes with from the factory, including plugs. By Audi plugs and replace them. If compression is good you and the plugs don't fix it, you probably have a bad injector

 

These are Audi NGK plugs. Guy in official Audi service put them, a month ago instead of original ones, that were faulty. But they are on vacation now, so I have to wait, or try with different mechanic.