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Q: Car ran fine. I parked it and this morning it has a misfire in cylinders 1,3,4.

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I'm having misfiring problems in cylinder 1,3,4. What could b causing this?

My car has 117000 miles.
My car has an automatic transmission.

A: This is a common question. We often want to...

This is a common question. We often want to assign an event like parking our car or filling our fuel tank to a specific failure. More often times than not, this is just a coincidence. My response to such a question is, why does a light bulb decide to fail? It just does. It is its time. In this case, with 117,000 miles on your vehicle, it is in need of some ignition system maintenance, if it hasn’t been done already. There are many possible causes for misfires, and determining what is causing yours requires my presence with your vehicle. Without that, I can give you a number of ideas.

You state you have misfires on cylinders 1,3,4. There are several methods of determining what cylinders are misfiring and more than a few things that will cause a misfire. Are you using a scanner to watch misfire monitors, or are you using another method? Is the car running bad, or did the Check Engine Light come on with codes and the car runs fine. These are two important details in determining what is causing your misfires.

If the car runs rough, I would want to know if the spark plugs and ignition wires have ever been replaced. If not, I would start there because they rarely last 117,000 miles and this is part of regular maintenance.

Another consideration and another maintenance item, is the timing belt. Has it been replaced yet? It is very common for an old timing belt to jump or strip on startup. When the cam timing is off, misfires will occur in multiple cylinders, as you have here.

Having multiple misfires suggest a common component failure. This points to either the timing belt or the ignition coil. But I am throwing things out there because I don’t know exactly what the symptoms are and if there are multiple cylinder misfire codes.

In summary, spark plugs, ignition wires, ignition coil, timing belt, ignition module, or PCM could be the culprit. PCM failures are rare. Unfortunately I can only give you a few ideas. This is not a replacement for an experienced technician making a diagnosis. I’d highly recommend having your vehicle looked at by a certified technician who can properly asses and fix your misfire problem.

Good luck.

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