My 07 G35 as begun to act a little strange lately. I have 67K miles on it and it seems to randomly rev up and down 100 rpm or so when at a stop light. Most of the time it stays solid at about 850rpm when idling.

Also, I've noticed that my mpg is less even on the highway. Same gas and driving style.
Any clues?

Would resetting the ECU help?

Thanks.

 

check around your intake piping and manifold for leaks...perhaps something loosened up over time