my 2003 1.8t jetta started blinking the engine temp light in the instrument cluster about a year ago, it only came on when it was cold and would idle rough and bellow out smoke.but would stop and run fine when it warmed up enough and the light would go off if you turned the car off then back on again. now its constant. i've changed the engine temp control sensor but no change. any help?

 

Thermostat? Is it still idling rough and blowing smoke? What color is the smoke and smell it too.

 

it not the thermostat because the cars not overheating, its just the idiot light in the instrument cluster, indicating that its a sensor somewhere in the system. the smoke is bluish thats why i said it's drinking fuel.

 

Could be your fuel pressure regulator and your getting a code for a rich air/fuel ratio.