2001 Subaru Other subject

2001 SUBARU
165,000 MILES
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WITTYFANTUM
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my check engine light came on a week ago, car seemed to be running fine until today. It is idling very rough, and when i step on the gas, it sounds like my exhaust is backfiring. So i decided to use my boyfriends code reader, I dont remeber the numbers, but it said cylinders 1 and 4 are misfiring. So i looked that up on the internet, and something about an EGR valve may need cleaning or replacing. What do you think?
Aug 26, 2013 at 11:45 PM
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CARADIODOC
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When is the last time the spark plugs and wires were replaced? The diagnostic fault codes never say to replace parts, only which circuit or system has a problem. An EGR valve is not likely to cause backfiring but worn spark plugs and wires will.
Aug 27, 2013 at 2:27 AM
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WITTYFANTUM
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OK, today my boyfriend decided to take a look at my car FINALLY, and he ordered an oxygen sensor for it.....he said my plugs are fine but he did clean the corrosion on the spark plug wires and said they are fine also....I REALLY hope this works, but i am having some doubts....are my doubts legit?
Aug 28, 2013 at 5:01 PM
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CARADIODOC
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Sorry for the delay. Been out of town for a couple of days.

The oxygen sensors will not cause cylinder misfires. They only report on what has already taken place with the fuel and air. In very rare cases a partially-contaminated O2 sensor may cause the Engine Computer to want to add a little fuel to adjust the mixture, and that extra fuel can overcome some other cause of a misfire like a partially-plugged injector. In that case the fix is to replace the injector, but replacing the oxygen sensor would also affect it.
Aug 30, 2013 at 4:34 PM