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I’m going to reignite this forum. I have a 2011 G37 with 170k miles. I’ve had a random intermittent P0300 misfire code only on cold starts for years. When checking with OBD fusion, it can have at least 1 misfire on any given cylinder, seems to be worse on 3, 4, and 5. I am still on the original ignition coils but I had another set with around 95k miles that I switched in but the result was still the same. I pulled the plugs after it sit overnight and those worst misfire pistons did appear damp on the top. It does not appear to be coolant cause the pistons are not “steam cleaned” like you would expect but the leak could be extremely small. I’m also wondering if I have leaking injector(s) that’s allowing fuel to seep into those cylinders overnight. If I pre-prime the fuel system before a cold start, it seems to have a higher RPM surge upon first starting. The car is completely stock with no modifications whatsoever. I have checked for Vacuum leaks, spark plugs only have around 15k miles, and has new intake filters. Any advice would be helpful! I have linked photos of Cylinders 3 and 4 which had the worst cold starts misfire. Car runs great other wise and does not misfire at all when warm. I have also linked a few pictures of the spark plugs which all looked about the same with a slight hint of a white coating but from what I’ve read, that could be normal.
Last edited by J_Smith-G37S; Nov 9, 2025 at 12:55 PM.
I’m going to reignite this forum. I have a 2011 G37 with 170k miles. I’ve had a random intermittent P0300 misfire code only on cold starts for years. When checking with OBD fusion, it can have at least 1 misfire on any given cylinder, seems to be worse on 3, 4, and 5. I am still on the original ignition coils but I had another set with around 95k miles that I switched in but the result was still the same. I pulled the plugs after it sit overnight and those worst misfire pistons did appear damp on the top. It does not appear to be coolant cause the pistons are not “steam cleaned” like you would expect but the leak could be extremely small. I’m also wondering if I have leaking injector(s) that’s allowing fuel to seep into those cylinders overnight. If I pre-prime the fuel system before a cold start, it seems to have a higher RPM surge upon first starting. The car is completely stock with no modifications whatsoever. I have checked for Vacuum leaks, spark plugs only have around 15k miles, and has new intake filters. Any advice would be helpful! I have linked photos of Cylinders 3 and 4 which had the worst cold starts misfire. Car runs great other wise and does not misfire at all when warm. I have also linked a few pictures of the spark plugs which all looked about the same with a slight hint of a white coating but from what I’ve read, that could be normal.
give me a call and I can discuss this with you and some solutions, i don't have the time to go into all the possibilities in a discussion thread, but you're welcome to call and discuss what some possible causes/solutions might be: vq37tt.com
give me a call and I can discuss this with you and some solutions, i don't have the time to go into all the possibilities in a discussion thread, but you're welcome to call and discuss what some possible causes/solutions might be: vq37tt.com
I appreciate the quick response! I considered reaching out to the number you had provided previously in this forum but where it had been several years, I didn’t want to assume you were still involved in the tuning/data logging process. I will absolutely reach out this coming week. Thanks!
