logicbeats

So I just put the intake manifold back on and replaced one of the vacuum hoses. I cleaned the throttle body as well. After assembly, the engine is running rough. I was getting a 301 code with a randomly flashing engine light. I replaced the coil. No change. When I first start the car, no problem. When the engine rpms come down, that's when the flashing engine light starts. Thanks in advance for any advice 02 A6 3.0

SloopJohnB@mac.com

Try moving the plug to another cylinder and see if the misfire moves. If it does, it's the plug. It could also be a leaking intake manifold gasket or some other hose got hosed (pun intended) along the way.

logicbeats

Perfect! Great idea.. thank you.

logicbeats

Switched the spark plug. Code went to 300, 301, 304

rocketman4321

Without matching the numbers to cylinders...check the driver modules mounted on the intake/air filter housing. You probably unplugged them to get at the manifold. I think P300 is a random misfire, which would be consistent with a loose connector. Each module drives the coil packs on one bank, so if the numbers match that's further evidence.