p0300 misfire detected, p0303 misfire cylinder 3

[vange_c4s]

hello everyone,

so i have searched on this topic but would appreciate current information. my car '03 c4s, stock. 18K miles, florida car now in new england. i have put 6K on it myself with no troubles. car sat for 11 days in my garage while on vacation, thru a new england heat wave 95+. started it up today to warm it for oil change and once up to temp it began misfiring/running rough at low rpm. cel flashed then went steady and i got a bring for service indicator in display. limped home. read codes and got p0300 misfire detected, p0303 misfire cylinder 3. cleared codes, started up again and same two codes came back. bummer. came here for research. clearly there can be many reasons for these faults, but i was hoping for an easy one. appears a common failure is the coil packs. jacked it up, and took a look at #3 coil pack. nothing appeared to be cracked. bummer. i was going to swap #4 and #3 to see if fault followed coil pack, but #4 does not look real easy, and if the fault moves i need to take the failed one off anyway. new coil packs around $50, so should i just spring for a new one and try it? should i let it sit tonight and cross my fingers when i start it in the morning? should i use freeze spray on it to cool it and see if misfire stops? should i be more worried? help!

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03 996 c4s

08 si coupe

99 540i six speed

84 audi gt coupe

73 saab ems

[Loren]

:welcome:

You are going about it in the right way. Swap coil packs with another cylinder and if the misfire does not follow the swap do the same with the spark plug.

Usually is one or the other as long as the electrical connectors are not damaged.

[vange_c4s]

hi loren,

thanks. your diy is such a great help when working on a new (to me) car. i have only had my new car for three months or so and still learning how to drive it! as far as working on cars; i am not the best mechanic, but can figure out many things. when the time comes for spark plugs i will inspect all the coil packs.

for this try i am going to swap #3 and #2 and hope the code moves. is removing the muffler preferred?

[Loren]

Depends on the size of your hands and what tools you have. Certainly doing the rear plugs (on each side) is very difficult without removing the mufflers.