Hi all, it’s my first post so if I’m not in the right section please redirect me.

So I bought a used g37 coupe with 200,000 km and the past 2 months it was running like a dream. A week ago however I noticed a big and noticeable power loss like 15-20% especially in lower rpm’s and something like a hesitation as well. My idle is also rough and fluctuates; and then I got the p300 code a few days ago. My mechanic recommends I should start with changing the spark plugs so I just wanted to ask; is there anything else that could be causing this power loss and code? A reply would be greatly appreciated!!

 

Random misfire. Mechanic is right. Maintenance. Plugs. Clean TB. Clean mafs. Idle relearn etc.

 

Thanks a lot for the reply friend!

 

At 200K km (approx. 125K mi.) your car is definitely in need of some maintenance. I can only imagine how gunked up your throttle bodies are. I would do all of the maintenance items PNW_IPL suggested including the obvious air/oil filter changes, etc.

These items are relatively easy for the home mechanic to do (if you are able) and would make for a good Saturday project. There are a few DIY threads on the forum to give you a idea of what is involved:

Throttle Body Cleaning
Changing Spark Plugs

Hope some of this helps!
Alex

 

I just replaced my plugs in my car at 157kms, and they were lookin pretty fouled... I would be floored if the original plugs are in the car, but such things do happen... also cleaned my TB’s at 156k, they weren’t bad but they were starting to collect serious gunk. Try these things and see what happens