a4buff19

a4 2013 manual 70k miles.. purchased used. has been fine except for water pump. Now has thrown this p0304 code. changed coil/s spark plugs. worked for a week. then EPC and engine light came on again car stutters.. if you turn it off and back on engine light remains on but car drives with no issues whatsoever. the only code that comes up is this code.. originally the low turbo code came up but that has been resolved.
I have heard that build up in manifolds might cause this? but only throws the one code any thoughts or other things i can try before i have it cleaned would be helpful.

JRB_brownA5

See my post on electrical gremlins.
Code P 0304 was one of the codes I got, along with P 2310 when the coolant valve problem pushed water up the wiring into the EPC connector.
Yeah, sounds super crazy but it happens that water travel up the inside of the wire insulation and mess up the car electronics

It is a relatively easy check. Pull the windshield washer reservoir filler and the cover off of the engine computer, then the computer connectors off of the computer.
And/Or check the connector at the coolant valve. Two pin connector going to a valve that has two coolant lines at the left side of the transmission bell housing.

my car is a 2013 with 80K miles and a manual.
Ultimately the misfire was caused by signals that didn't correctly make it to the coil so swapping the coils around didn't fix my problem.

I'm tossing out this potential cause a bunch because I wonder how common it is.
Ultimately I figure Audi ought to do a recall on the car same as they did for A8

Mikhail94

I have the same issue. Swapping coils, spark plugs, injectors and cleaning valves didn’t help. I did find Coolant in the valve you mentioned. I need help. Help please