Q: I changed the spark plugs and coil bar on my 2014 Chevy Sonic. The engine starts, but it won't go over 3,000 RPM. Did I do something incorrectly?

A: Given that this happened immediately after you worked on the car, I'm going to put my money on "yes." It might not have been your fault, but I'm guessing that something's wrong with the spark plugs. If they can't make a big enough spark, the engine might run fine at lower speeds but fail when you try to rev it up and need that bigger spark.

You've heard of spark plug gaps, right? The manufacturer determines how much space there should be between the spark plug's two electrodes. That determines how far the spark will jump and how big a spark you get.

Most spark plug gaps are somewhere in the range of 1 to 1½ millimeters. When we install spark plugs, we always check the gaps. Why? Well, some come out of the box perfect. But some don't. Who knows why? Maybe someone dropped a crate of them while they were unloading. Or maybe you dropped one on the garage floor.

The size of the gap is very important. If it's too small, there's not enough room for the spark to jump. So the spark won't be big enough and hot enough to combust all the fuel and air coming into the cylinder when you rev up the engine. Conversely, the amount of air turbulence in the cylinder grows as the speed of the engine increases, so if the gap is too big, the spark can get blown out at high speeds.

You can buy a gapping tool at your auto parts store for less than $10. And then you'll have a working car and a new hobby. But before you do that, check to make sure that you bought the correct plugs for your car. Using the wrong plugs also could cause this problem. And if there's any question about whether you've got the right plugs, get them at your Chevy dealer's parts counter. That'll guarantee that you're starting on the right foot.

Seasoned advice on salt

Q: I'm on a six-month visit to the East Coast from my home in the Pacific Northwest and brought my 2008 Toyota Tacoma with me. I'm scared of all the salt on the roads and what it might do to my truck's virgin undercarriage. How do I prevent the salt from settling in and doing its oxidizing worst? And, is going to those fancy car washes sufficient to keep my "Silvie's" under-regions tidy?

A: You're absolutely right that the salt used on the roads during the winter wreaks havoc on cars. It causes the cars and their parts to corrode more quickly than they would otherwise. Being in the car repair business, I very much appreciate that.

Given the brief length of your stay, and that the bulk of it will be before the worst of winter sets in, you can minimize the effects on your truck. The roads get salted when there's a snowstorm, and that creates a salty, slushy gruel that gets splattered all over your truck — particularly the undercarriage and fender wells. It's the gruel that you want to get off.

The best approach is to wait a few days to a week after the storm. By then, the roads have dried out, and while there's still salt on the roads, your tires aren't slinging a wet slurry of salt all over the bottom of your vehicle. Go to a car wash and pay for the optional undercarriage cleaning.

Some salt still will get on the underside of your truck after that — you can't avoid it — but the worst of it collects during those first few days after a storm. To remove the residual salt, get a car wash every few weeks, even if it doesn't snow.

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