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Brenden Young

Brende ... 5/24/2018

2009 Audi A4 Quattro Base 6 Cyl 3.20L


Misfire when under load

Have a question for you all, my car started to misfire under load today. EPC and MIL light flashed until I let off. I then turned car off and on. epc was only light on. Scanned for codes. None. Let car sit. No more epc light however under heavy acceleration it's extremely rough and missing and continues to mis even at idle until I restart the car. Any one have similar issues? Starts to misfire around 3000 rpm. Car drives completely normal until I about 3/4 throttle or above 3000 rpm. One of stars missing though it will mis fire until I restart car. Even at idle once it's misfiring it shakes really bad.
I replaced spark plugs, engine air filter and changed oil 2k miles ago. Checked that the spark plug connections are good they look fine. I think it's a sensor due to it by missing until I induce the symptoms and then it will continue after that. Ideas?

1 Answer


Jimm 5/28/2018

For the misfires; P0300 = Random Cylinder Misfires

It may mean that one or more of the following has happened:

Engine vacuum leak
Faulty spark plug or wire
Faulty coil (pack)
Faulty oxygen sensor(s)
Faulty fuel injector
Burned exhaust valve
Faulty catalytic converter(s)
Running out of fuel
Poor compression
Defective engine control computer (ECM or PCM)

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.

If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.


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