Don't want to doubt you, but I'd definitely check to make sure it feels lightly oily or even soak some a few drops into a paper towel and see if it ignited (careful of course). Assume it's not running rough / missing occasional firings, right?
This can also be caused by a defective fuel pressure regulator. (Ford Ranger)
potato with in whistle in it, jammed into the exhaust pipe?
When a weird noise comes from the exhaust after stepping on the gas pedal, it could mean that there is a hole in the exhaust pipe. Sometimes the exhaust pipe will rust and need to be replaced.
That would depend what is being exhausted from Natural gas/ OIL # 1,2 ,4 or 6 HUH?
backfire timing off
bolt it on the motor
because your gas tank is in the center
Exhaust of an engine is a gas.
incorrect engine timing so that it misfires
Exhaust Gas Recirculation. A small amount of exhaust gas is fed back into the cylinder to lower combustion temperatures and lower tail pipe emissions.
EGR (Exhaust Gas Recirculation) look for it to be attached to the exhaust manifold or a pipe from the exhaust manifold
If its smells like gas, you are putting too much gas in the engine and some is unburnt and going out the exhaust. Exhaust underneath means there is a leak in the system somewhere. If there is no louder noise or hissing, I would expect the catalytic converter is leaking. Have it checked and get a tune up. http://www.autozone.com/servlet/UiBroker?UseCase=S001&UserAction=viewSimpleDiagInfo&Parameters=info answer bad exhaust pipe