Don't Ignore Check Engine Light on Rough-Driving Volvo

Dear Car Talk:

I have a 2004 Volvo S60, grayish-green, with an engine problem that has occurred three times. It happens when the engine is warm. After I've made a brief stop (like for shopping), the engine will start, but runs very rough. Then, when I start to drive, I cannot get the car to go more than around 20 mph, no matter how much I press on the gas pedal.

My "check engine" light comes on, and I get a message saying "poor engine performance." When I come to a stop, I put it in neutral and the engine surges. I've managed to get the car home all three times, and the next morning, the engine runs fine, though the check engine light and the performance warning are still on.

Eventually, the light and warning go off, so I haven't taken it to a mechanic. What do you suggest? -- John

I suggest taking it to a mechanic, John.

I love it when you can't go more than 20 mph and the engine is sputtering, and you get a helpful message on the dash that says "poor engine performance." Well, duh!

But here's why a trip to the mechanic is essential, John. Whenever your check engine light comes on, your car's computer stores a fault code.

With the help of a scan tool, your mechanic can then read that stored code and know exactly what caused your check engine light to come on.

My guess is that your electronic throttle module is failing. The throttle is the mechanism attached to your gas pedal that regulates how much fuel and air are sent into the cylinders.

In the old days, the throttle was connected to the gas pedal by a cable. But now it's done electronically. An electronic signal tells the ETM the exact position of your gas pedal, and the ETM then operates a servomotor to open and close the throttle.

Volvo had a problem where the contacts inside their ETMs were wearing out and causing the exact symptoms you describe, John. They even extended the warranty on those ETMs for a bunch of cars to 200,000 miles. Unfortunately for you, it's 10 years or 200,000 miles, so you're about seven years late in getting to your mechanic. Keep that in mind next time you ignore your check engine light, John.

Anyway, once you get the car scanned and confirm that the problem is the ETM, you might want to call your Volvo dealer and ask if you're eligible for any help in repairing the car. They might tell you to go pound Swedish meatballs, but it's worth asking. Then compare the repair price at the dealer to an independent Volvo garage and go with whichever is cheaper.

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