Q: Car engine shaking like a lawnmore and white gas coming from exhaust

Your car is misfiring. The white gas is most likely steam. The smell is the catalytic converter working to hard from unburned fuel entering the exhaust system because of misfiring. Your car needs to be diagnosed to figure out what is causing the misfire.

Misfires occur when the ignition system is unable to ignite the fuel that is sprayed into the cylinder. The first question is which cylinder or cylinders are misfiring. With your newer vehicle, the best way to determine which cylinders are affected is to look at the misfire counters on a scanner. Keep in mind the code reader that most auto parts stores utilize is not the same as a full function scanner. Scanners are very expensive and complicated tools. If you don’t have a scanner, I would use a test light to short out the cylinders one at a time. Doing this can be tricky and is best demonstrated, so if your not aware of this technique, I recommend you have someone else help you with this. Either way, determining which cylinders are misfiring is your first step.

If you have access to a scanner, if you know how to read all the data, often times we can make a determination about what is causing the misfires. This requires an in-depth understanding of all the electronic systems on your car. If your not very experienced with this information, I recommend you booking an engine is misfiring inspection in order to have this diagnosed correctly.

The diesel smell from the catalytic converter is a result of unburned fuel because of misfiring. Catalytic converters chemically burn HC’s (hydrocarbons) that internal combustion motors naturally create. When unburned fuel, (which is the definition of a misfire) occurs, the chemical reaction inside the catalytic converter becomes out of control and can actually start a fire. If this possibility exists, your Check Engine Light will be flashing. The smell is a precursor to this possibility. Anytime your Check Engine Light flashes, I highly recommend not driving the car. I have seen several customers cars burn to the ground because they did not heed the flashing light.