Hey guys,

I have a misfire problem on my 02 A4 3.0 that recently started and any help I can get would be greatly appreciated. I recently got a multiple cylinder misfire code (300, 301,302, 303, 304, 305,and 306) all of this just sort of happened over night. My problem is that once the car has had a chance to sit over night and completely cool off it runs just fine. But, the second the thermostat opens up the car goes to crap. I'm assuming it has to do with a sensor that deals with Open/Closed loop tuning. I do have a small coolant leak coming from the water-pump seal at the moment but its a very small leak (less than a quart every 4 months) and don't have enough money to fix. I have cleaned the MAF, replaced the engine temp sensor, checked the coil packs (all seem to be working ok, but who knows) tried unplugging the primary o2 sensors, checked for vacuum leaks (which I did have and thought I fixed) and still the car runs terrible once it warms up. I am at a complete loss as to where I should even look next. If anyone has ANY ideas I am completely open. THANKS!

 

What works with mine is I replace the coolant temperature sensor, try that, it's like 10 bucks.

 

The little green on in the back of the motor under the intake tube? If that's the one you're talking about, I did that already. If you're talking about something different, could you please elaborate as to where that sensor is?

 

replace the ht leads i had the same fault

 

Yes that the sensor I was referring to. Mine gives me the opposite problem, the missfire occurs when it's cold. Check your wiring harness, an open wire could cause this weird missfires when hot.

 

i am having the same problem, did a tune up on my car and now when it warms up the car runs rough like the plugs are misfiring. please help.

 

What/Where are the HT leads? I'm kind of a simpleton when it comes to all these connections and sensors

 

well the ht leads are from the coil pack to the spark plug thats ht leads the carbon inside them break down and sometimes when the car gets warmer they breakdown ,condensation inside them maybe has your 3 litre audi got leads if so change them there about £50

 

That would cause every cylinder to misfire? So I should replace every coil pack?

 

if u never replaced your coils then its definatly a good time to do so.