Hello everyone, this is my first post ever so I'll try to be as professional as possible with no mechanic background. I have recently ran into a huge problem with my 2003 Audi A4 1.8T Quattro. So far I have changed my head gasket, timing belt/water pump, thermostat housing, coil pack on 2 cylinders, and fuel injector on cylinder with misfire.

Symptoms
- Engine starts, misfiring immediately with cold start. (cylinder #3)
- significant amount of smoke coming out the exhaust (not coolant, smells like gas)
- Does not smoke if fuel injector 3 is unplugged (cold or warm)
- Stops misfiring after engine warms up (10-15 minutes)
- Engine misfire only happens when car has cooled down for hours

The problem appears to be a surplus of fuel being dumped out of fuel injector 3 only while the car is cold, and returns to normal after the car warms up. Could wiring cause this kind of problem to one specific injector? My mechanic seems to think at this point it's got to be either wiring or the ECM, I'll be scanning the car again today with vagcom, so i'll post the codes soon. Any help would be greatly appreciated, this headache has been going on for weeks now. Someone please help!!!

 

Your mechanic is an idiot.

Swap the injector with cylinder 1. And while its out soak the tip in carb cleaner for 30 minutes or so.

If the misfire moves its not a wiring / ecm problem.
If the misfire goes away its a problem with carbon and a sticking injector..... Which you can ride out until it happens again or just replace the injector