Sputtering? It’s likely an ignitionsystem problem

Dear Car Talk:

I have a 1989 Pontiac Grand Am LE with a 2.5-liter engine. The car has 154,000 miles on it. I can accelerate slowly and it runs fine, but if I step on the gas, it sputters and backfires through the throttle body. It does the same whether I am driving or standing still. I put new plugs in, but it didn’t help. I never get a check engine light. I bought the car new, and have maintained it properly. — Robert

You might not get a check engine light because the bulb may have burned out during Obama’s first term, Robert.

You might check to see if it lights up when you turn the key to the “run” position (just before you turn it all the way to “start”). If it doesn’t light up then, the check engine light isn’t working anymore.

Regardless, your sputtering probably is caused by a weak spark. If the spark is weak and you try to run the engine fast, the combustion gases inside the cylinder will actually blow out the spark. Then, instead of an explosion, you get nothing. And when you’re getting nothing from some of your cylinders some of the time, the engine will sputter, cough and lurch.

A weak spark almost always is caused by a secondary ignition problem. The secondary ignition system is the high-voltage part of your ignition. It includes things like your distributor, coil, plugs and plug wires.

You’ve already replaced the plugs. If I were a guessing man, I’d probably try a new distributor cap, a rotor and new plug wires next. Those are pretty cheap.

If that doesn’t work, my next guess would be a coil, followed by a new or rebuilt distributor. Those are not so cheap. So, you may want to have a mechanic do the guessing for you, since he can try things and then put them back on his shelf if they don’t fix the problem.

I hope your sputtering days are numbered, Robert.

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