When the car is cold and i try to start is working like the old beetle.when is hot is good.why?

Try replacing the water temperature sensors. Sometimes there are 2 with one working the dash and the other working the engine. You are probably running too lean. The "cold start sequence" kicks in at a cold to warm temperature. If the sensor is stuck on hot it will be too lean to start.

You might try a new thermostat that may be more responsive than your old one. Check air filter for condition.

http://www.redlinemotive.com/replacement/volkswagen/blowermotor.asp. Hope this helps...

try the cold start sensor/ automatic choke

That is an over temperature indicator. It means your car is running hot.

This is the sensor that control cold start up idle just like a choke use to do on the old carborated systems. It allows for the car to idle slightly higher and tells the ccu to adjust the air to fuel ratio for cold starting. Since it is a volkswagen it could be rather expensive.

you need to have someone look at it that knows vw a/c systems
there too many things that could cause this to start guessing

IF I DONT RUN DG GAS DRYER IN MY 98 BEETLE , AND MOTORCYCLE PATTERN OIL , MINE WILL NOT ACT RIGHT , AND THIS CAR RUNS PERFECT EVERY DAY EVEN IN -40 TO -50 TEMPS SOMETIMES , IN ALBERTA, TRY MOTUL 300V OIL , 5W30, AND GAS DRIER , THESE CARS HATE MOISTURE IN THE FUEL , ALSO TRY NOT TO RUN PREMIUM GAS , BECAUSE NOBODY BUYS IT , THE CAR WILL GET A TANK FULL OF WATER, MY CAR HAS 89000 MILES ON IT AND WORKS BETTER THAN MOST NEW ONES, HOPE THIS HELPS, EVEN IN THE SUMMER RUN GAS DRYER EVERY COUPLE TANKS , DONT NEED MUCH, THE TACH WILL SMOOTH OUT QUICK,ALSO IF ANYONE NEEDS A BLOCK HEATER FOR A 2.0 LITRE BEETLE , MINE HAS ONE FOR A GOLF , AND WORKS PERFECT, ALSO THERE IS AN OIL PAN HEATER THAT I HAVE ALSO , IN CASE IT WAS NEEDED.

if you have a maintance free battery check the eye in it if green its okay.if dark or black .battery no good that cause car to quit.if battery good you got a ignition component problem.

Try changing the engine temp sensor. The sensor will be telling the ECU that the engine is hot when actually its cold. therefore the fuel mixture will be weak.I this doesnt cure it, i would be looking at fuel starvation. Faulty of cracked fuel pump or just maybe run out of fuel.

TL

The issue of hot no start is often the crank shaft position sensor, do you have any trouble codes, if you want a free test Kragen auto will do it for you. Let me know what comes up if anything.