07 pontiac wave help! (gas mileage has dropped)

[sflindall26]

i do sometimes get a burnt oil or burning wax smell coming through my vents when the car is it idle after driving.

could cam timing be the problem?

I recently just had this problem as well, it was caused by oil leaking from my valve cover seal on to the manifold and then the oil would burn off causing the burning smell to come through my vents when the car would idle.

[rrb6699]

its something. I found all kinds of black carbon gunk in my intake manifold, etc, but when I removed the head piston tops have been totally caked with it. it is enough to affect the pre and or catalytic converter . whats the best way ro clean tops of piston heads.

either this is result of the wrong spark plugs or low octane fuel. how can it be prevented? I don't know if I can trust 93+ octane because of how long it may sit since everyone buys 89. I never liked additives so wouldn't know what to use or if any would work with this engine.

I do know fuel burn is not efficient.