Should the throttle body casing be cleaned regularly?

Dear Car Talk

Dear Car Talk | Mar 01, 2001

Dear Tom and Ray:

Help. I'm afraid of my car. I have a '91 Chevy Camaro with a V-8 engine. The car is in good condition and has been well-maintained. The other day, I was returning to the office from lunch and accelerated up an overpass. Suddenly my car felt funny, and the engine started racing. Applying the brakes did nothing to slow the car. I have heard of people having their gas pedals stick, so I applied the brakes with my left foot while trying to lift up the gas pedal with my right foot. The pedal did not appear to be stuck. I then looked around for something soft to crash into, like a bush. I headed for a parking lot, simultaneously applied the brakes and the parking brake, and shut off the ignition. The car stopped in a parking space. I then had it towed to the Chevy dealer, who fixed it for a small charge. He said the problem was excess carbon deposits in the throttle-body casing that had made the throttle plate stick. He told me that these things should be cleaned every 30,000 miles or so. I don't recall seeing that information in the maintenance guide -- and besides, I'm a girl, so why would I know this? I am now afraid when I drive the car. Sometimes I still feel it "catch" when I speed up. Is there anything else I should check? -- Gina

RAY: First of all, you can't drive into a bush these days, Gina. The Secret Service will be all over you in no time.

TOM: If you still feel the accelerator sticking, Gina, then the other thing to check is the throttle cable. And actually, I wouldn't even bother checking it, I'd just replace it. Considering how cheap it is (25 bucks) and how dangerous a frayed cable can be, I'd just ask a mechanic to replace it for you.

RAY: The cable is made up of a strand of twisted wires, all housed inside a plastic sheath. And when the cable gets old and starts to "unwind," it's very easy for it to get stuck against the inside of the sheathing. And my guess is that that's what happened to you.

TOM: And in that case, pulling the gas pedal back would have no effect at all, since it's the cable, rather than the pedal, that stuck.

RAY: While you're in the shop, you should also have your mechanic check the cruise-control cable and the transmission "kick down" cable. Both of those are also attached to the throttle body and can cause unwanted acceleration. If either of them show any signs of hanging up, have him replace those, too, just for peace of mind.

TOM: And by the way, for everybody reading today, the proper action to take when your accelerator sticks is to put the car in Neutral.

RAY: Once you turn off the ignition, you lose your power steering, your power brakes and, in many cases, your steering wheel will lock up. And when you're booming along at 60 mph, that stuff will only make a bad situation worse. So put it in Neutral first, and then turn off the ignition only after you come to a safe stop.

TOM: And by the way, if you put a racing engine in Neutral, the engine will continue to race -- it might even sound like it's screaming. You might even damage the engine. But at least you'll be able to steer and stop normally. And which is more important, your engine or your life?

RAY: Well, it depends. Is it a brand-new engine?

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