Intermittent problems are difficult to diagnose. Here's how you can help your mechanic figure the problem out.

Dear Car Talk

Dear Car Talk | Feb 01, 2001

Dear Tom and Ray:

I drive a 1987 Ford Escort. The car runs well, except that every three or four months it fails to start. If you leave it for a few hours and then try again, it starts right up. It happens whether the engine is hot or cold. I've had it checked by almost everybody, but no one can identify the problem. The last mechanic replaced the fuel pump and the fuel-pump relay, but no luck. Can you help? -- Bill

RAY: Intermittent problems are the hardest to diagnose, Bill. For instance, every six or eight months my brother will say something that makes sense. But since it happens so infrequently and so unpredictably, we've never been able to figure out why. And the same is true when you tell your mechanic that a problem occurs only once every few months.

TOM: So you're going to have to help him diagnose it, Bill. When I think about things that cause intermittent starting problems on this car, the first part that comes to mind is the electronic-ignition module (EIM), which would prevent the spark plugs from sparking.

RAY: We have a little "spark checking" device for problems like this. It's a little box that goes between the spark plug wire and the spark plug, and it lights up whenever the spark plug "sparks." If you can find a mechanic who has one of these, have him lend it to you. Then, the next time your car won't start, you check to see if the light is lighting up while you're cranking the engine.

TOM: If you do see the light flashing, then you DO have spark, and your problem is fuel related. In which case, since you've already changed the fuel pump and relay, it could be the car's computer.

RAY: But if the lights don't light up, and I suspect they won't, then my first guess would be the EIM, which costs about $100. But before you pay for one, ask your dealer if yours is covered under the recall -- Ford had to recall about a gazillion of these a few years ago. If that's not the problem, my second guess would be the distributor itself, which will also cost you about $100 for a rebuilt one.

TOM: And his third guess is alien intervention, so hope that one of his first two guesses is correct, Bill.

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