Where there is smoke, there might be an air intake test

Q: I have a 2013 Hyundai Elantra with 84,624 miles. The dealer recently replaced the engine under warranty. When I picked up the completed car, the check engine light came on within a couple of miles. I took it back, and they found a vacuum leak trouble code and needed to get a smoke tester to find the leak. They told me the problem was a contaminated "evap" canister. I am wondering if the smoke test could have contaminated the system or if that was even the problem.

— K.K., Chicago

A: No, the smoke machine did not contaminate anything. These devices, which have been around for years, inject harmless smoke into the fresh air intake system of the engine. This is where vacuum leaks occur but are very hard to find. Any “false air” entering the engine causes performance problems. By filling the system with smoke, the leak reveals itself as it curls from the leak. Easily spotted, it can be quickly repaired.

Q: I use 92-octane nonoxygenated fuel in the tank of my 1971 Jaguar. Do I need to add a fuel stabilizer for winter storage?

— M.B., Hopkins, Minn.

A: Yes. Stabilizers keep the fuel fresh, much as a refrigerator keeps food fresh. It doesn’t matter what the octane is or the amount of ethanol (or other oxygenate) in the fuel. After adding the stabilizer, run the engine for about 10 minutes to distribute it throughout the system. This is especially important for engines with carburetors, because fuel sitting in the float bowl gets gooey and can also gum up the carb’s passages.

Q: Is any car company still manufacturing small to midsize SUVs, not crossovers? It seems the latter is being used interchangeably with the former. I am currently driving a 2006 Jeep Liberty. It's only a matter of time, I'm afraid.

— P.O., Montgomery, Ill.

A: To the best of our knowledge, there are no popular midsize SUVs built on a true ladder frame. Only the large SUVs built on the company’s corresponding trucks feature the traditional body-on-frame. Unless you do a lot of off-roading or heavy hauling, a crossover SUV should be more than adequate, and you will get decent fuel economy.

Q: Sunday's column (12/3) recommended applying silicone to the rubber seals on a moon roof. What silicone product would you recommend?

— R.H., Chicago

A: Good question. Although there are many things with silicone in them, we were using verbal shorthand for silicone lube. It is available as a gel or in aerosol. We use it on all door and trunk gaskets, not only to keep them supple, but to prevent them from freezing shut when a humid day turns into a frigid night. It is nearly impossible to open a door when ice forms between the metal and its gasket.

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