Why is gas leaking out of my muffler?
Because the engine has an over-rich condition that is causing liquid fuel to pass completely thru the engine and get pumped out the exhaust. This is an extremely dangerous condition for many reasons.
1 - leaking fuel in a usually hot exhaust system can ignite, explode its fumes under the vehicle, or subject passengers to hydrocarbon fumes,
2 - if enough fuel is in the exhaust to leak oiut a muffler...and it came thru the engine, there is a distinct possibility of internal engine damage occurring at any time. The pistons normally compress a mixture that is more than 85% air. Air is compressible (meaning you can make it physically smaller by squeezing it at great pressure). Liquids by their nature ARE ABSOLUTELY NOT COMPRESSIBLE!!
What this means is if you have a leaking fuel pressure regulator (kinda common on older ones) or leaking/stuck injectors (less common but still happens) or simply a defective fuel control system that is commanding ridiculous amounts of fuel (rare!), if it exceeds the compressible space in the cylinder for incompressible fuel volume,,,something will break or bend and quite possibly destroy the engine.
3 - if you have enough gas to flow liquid out the exhaust, you are at the very least damaging the catalytic converter which can run hundreds to even a couple of thousand dollars to replace. Further, your mileage is AWFUL right now because despite what people think, cars run on very small volumes of fuel. as in an eyedropperfull per rpm. Now imagine 100x normal fuel useage. Thats probably what you have to have it leak out a muffler. Think prevention, in addition to destroying the engine, it kills mileage, performance, detsroys cats and O2s, rings, seals, valves, sometymes purge systems or pcv systems. It should be repaired asap to prevent more costs si\oon.
2000 Ford Taurus
on May 04, 2015