We have a Chevette It runs fine most of the...

Dear Car Talk

Dear Car Talk | Jul 01, 1994

Dear Tom and Ray:

We have a 1984 Chevette. It runs fine most of the time, but every now and then, when driving at speeds of 45-60 mph, it will slowly lose power. You can press the accelerator to the floor, and it will drop to about 25 mph and then stall. When this happens, we usually pull off to the side of the road and wait about five minutes. After that, it usually starts fine and drives without difficulty. Since this problem never happens in a predictable fashion, we haven't been able to demonstrate it for any mechanics. Can you give us any suggestions?

TOM: Gee, Kelly. An '84 Chevette that's losing power. You need help. You don't have much power to lose!

RAY: There are several things that come to mind on a car of this age, Kelly. The most obvious is that the engine is not getting enough fuel. A dirty fuel filter could cause that. So could a weak fuel pump.

TOM: Another thing that could cause fuel deprivation is a faulty fuel tank ventilation system. When the system that captures fuel tank vapors gets plugged up, it can create a vacuum in the tank, which can starve the engine of fuel.

RAY: But believe it or not, I'd say the most likely cause of your problem is in the exhaust system. If your catalytic converter is partially plugged (which would not be unusual for a car of this age), the exhaust inside the engine might not be able to get out when you're travelling at high speeds. And if the exhaust can't get out, there's no room in the cylinders for new fuel and air to come in. And voila! The car stops running.

TOM: Have your favorite mechanic start with the fuel filter because that's easy and cheap. Then I'd check the converter, the fuel pump, and the fuel tank ventilation system in that order. Good luck, Kelly.

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