Old, stinky engine needs to be brought up to date

Dear Car Talk:

I live in California, and my husband has a '46 Ford. It has a terrible exhaust smell that permeates the area, and every time he starts the truck, I feel like it's harmful to our health. It comes through the windows in the house, and our clothes smell like it. Is this dangerous to our health? – Lola

RAY: Of course it is. What that truck is sending out its tailpipe in the first five minutes probably is equivalent to about 100,000 Toyota Priuses. What you're smelling probably is burning oil, unburned hydrocarbons and perhaps some vaporized free-range dinosaur cartilage mixed in there. It's more commonly known as "air pollution."

I would guess that the truck has one of two problems – or, more likely, both of them. The first problem is that it’s probably burning oil at a faster rate than the Saudis can pump it. That creates a bluish-gray smoke with a very acrid odor.

The other problem is that the carburetor could be pouring way too much gasoline into the cylinders, causing the engine to run rich and send unburned gasoline out the tailpipe. That usually creates black-colored smoke and a gasoline odor.

Now, we don’t want to be punitive here and take away the pleasure your husband gets from his ’46 Ford, Lola. Besides, if we did, he might take up a hobby that wafts something even less pleasant in through your windows – like the sound of him learning to play the trumpet. But he really should figure out what’s wrong with the truck – with the help of a mechanic if need be – and then fix it. Even fixed, the tailpipe emissions will be much worse than those from a modern-day car, but it shouldn’t smoke you out of the house.

If it’s burning oil, he probably can fix that with a ring job. In fact, the truck may have already needed a ring job when he plucked it off the set of “Green Acres.”

And if the carburetor is flooding, he can have it rebuilt: He can simply remove it from the manifold and ship it out to a rebuilder. Then you can surreptitiously change the return address so he never gets it back!

But if you guys are lucky, and he rebuilds the engine and the carburetor, you could cut down the tailpipe emissions to something in the range of 25,000 Priuses. And you might be able to live with that.

The fixes – especially the ring job – will be expensive. But you might point out that the cost of losing half of his assets (including half of the truck) to you in a divorce settlement will be much greater than that. Good luck, Lola.

Car gets a shimmy while idling

Dear Car Talk:

I have a 2007 Scion TC with 87,563 miles on it. Recently, it has started to shake while idling at a stoplight – or anytime I stop the car and leave it in drive. One person advised me to switch out the old spark plugs. I switched them out, but I still have the same problem. Any advice? – Ann

RAY: Don't switch out the spark plugs, Ann. That was actually a reasonable guess, if not a very scientific one. The person who advised you to change the plugs assumed you had an engine misfire, and guessed that the spark plugs might be the cause. Apparently, they're not.

If you came into the shop, I’d try to approach it more logically. Yes, that’s an enormous challenge for me, but I’d try.

If your check engine light was on and was indicating a misfire, I’d start by making sure all four of your cylinders were firing correctly. I’d do that by disabling one spark plug at a time.

When you disable a spark plug, you force the engine to run on three cylinders. So if the engine is running properly, each time you knock out a plug, the engine should run much worse – badly enough that it’s immediately obvious. But if you disable a spark plug and nothing changes, then you know that cylinder wasn’t contributing in the first place.

Then you just have to figure out why. It could be a bad coil, a faulty fuel injector, a vacuum leak or something worse.

If the check engine light isn’t illuminated, and all four cylinders are running well, then I’d suspect a weak or broken motor mount. Motor mounts are the heavy rubber-and-steel contraptions that attach the engine to the frame of the car. Their job is to both hold the engine in place and isolate the engine’s vibrations from the rest of the car.

So if one of your engine mounts is broken or badly worn out, you’ll feel the normal vibrations of the engine much more strongly. And you’ll notice it most at idle, when you don’t have all the other wonderful road noises and vibrations to distract you.

So take it to a good mechanic and ask him to diagnose it for you. He’ll figure it out.

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