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1997 subaru legacy GT

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Apr 14, 2015, 7:12 PM

Post #1 of 2 (875 views)
1997 subaru legacy GT Sign In

So I have a question. My car is throwing codes for both knock detonation sensor and o2 sensor are bad. I haven't noticed a loss in power but the car has probably had this ussue since I got it. So it could have a loss in power. Only thing that I am noticing is lately a rough or not stable idle, I start my car once and it starts perfect. I try again and it stutters,, turn it off try again and it starts up fine, turn it off and try it again it sorta stutters in RPM's. Its really inconsistent. I haven't had the car long enough to notice if im getting bad gas milage because in comparison to my last car it is getting awesome mileage. I do notice a strong odor from exhaust almost like fuel. Meaning it is getting to much fuel which I have heard is related to the bad knock sensor. I just want to know which one I should try replacing first that corresponds with my symptoms. My car start everytime, its just iffy on the idle when doing so. And it gets better as the car gets warmer. Its also throwing codes for misfires in cylinder 3/4 every other time I run the obd2, so maybe a spark plug change aswell? Somone said pil might be leaking into one of the spark plugs, and I have noticed a smell of oil burning somewhere in the engine bay, but very minimal because I don't lose very much oil at all. Barley have to add any between 3000 mile oil changes. 1997 Subaru legacy 2.5 gt. TIA.

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nickwarner profile image

Apr 15, 2015, 8:15 AM

Post #2 of 2 (852 views)
Re: 1997 subaru legacy GT Sign In

First, realize that codes are not a magic ball and do not tell you that a sensor or other part is bad. There are upwards of 20 different codes related to an O2 sensor but most do not even indicate a bad sensor. The codes point to a circuit and give a direction to look in. They are a start to a diagnosis, not a diagnosis in itself.
On an OHC engine the plugs are down in some wells in the valve cover. The gasket has seals that go around each of those tubes. If they leak then oil gets down around the plug and shorts it to ground through the block instead of the full power going through the spark plug. You should look down the wells and see if this is happening. If it is, a new valve cover gasket will be needed, and you should change the plugs and wires while you are in there. If there is a lot of oil in the plug tube, you should suction as much out as you can before you pull the plug out so you don't dump a bunch into the cylinder. If a lot of oil is in there, you could potentially hydrolock it when you go to start it later. At minimum it will smoke like hell for a few minutes.
You are smelling fuel out of the exhaust because you have a misfire and that gas didn't get burned in the cylinder. It is important to fix that before you damage your catalyst from the raw fuel entering it or wash down a cylinder with fuel and wipe the rings out. Also, some of the fuel will wash down into the oil so when you are getting rid of the misfire you should change the oil. Oil watered down with gasoline doesn't lubricate well and will wreck the rest of the motor.
Check out the plug wells and condition of the spark plugs, and also please post back with the exact code numbers you are getting so we have a direction to go with the diagnosis.

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