2004 Nissan Murano P0300 Code

[Ryan]

Hey all, wondering if anyone can help. Got a service engine light about a month and half ago, along with some roughness at idle when the car is cold. Went to autozone to get the readout: P0300 random misfire. Figured the car had about 85k miles and just needed a spark plug change.

Had a mechanic replace the plugs and he said the seals (assuming valve seals?) were allowing oil to get onto the plugs and could cause a potential fowling. I didnt have time for him to replace everything at the time so I only replaced the spark plugs.

Fast forward a month later, engine rough at idle on initial startup and the service engine light back on. What do i need to do? How much will it cost (DIY Vs. Mechanic)?

Thanks!

[njjoe]

Ryan-

Welcome to the forum.

The following excerpt is from the 2005 Service Manual:



-njjoe

[smendoza]

I've had a similar issue twice in the past 6 months. Both times it turned out to be a faulty coil pack (different cylinder each time). Checking codes was usually a mixed bag - half the time I would pull the random cylinder misfire, the other half I would get a P030X (where X=cylinder number). Pulled the coil pack for the cylinder that was misfiring and could see that the plastic was charred and pitted right above the rubber boot portion that seals to the top of the spark plug. I bought replacements at Advance Auto Parts (~$75 each, limited lifetime warranty - buy online and pick up in store and you can use promo codes to get a pretty good deal).

My first one went bad on cylinder #2 - since this was the front of the engine and easily accessible, I only changed this one alone. The next one was cylinder #5 - while I had the intake plenum off, I went ahead and changed all three on the back side of the engine. There are instructions in the forum here for the rear coils/plugs; the removal and replacement of parts to get to them is not as terrible as it seems.