Po302 Misfire
03-17-2019, 10:20 PM
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Po302 Misfire
My 2005 lsj has a P0302 cylinder 2 misfire. It is tuned for 94 octane and I ended up having to put a full tank of regular 87 with STP octane booster to bring it up to a reasonable octane level. (I know I shouldn’t have put regular but I was far from home) about 4-5 hours down the road I started to get a misfire (blinking check engine light). I burnt about half the tank of regular then topped up with 94 octane and it stopped misfiring for about 10 minutes. Then I took it downtown and it started misfiring again and hasn’t stopped since yesterday. I tried wiggling the injector harness and no change, any advice to where I should go from here would be great! It has NGK 1 step colder plugs and zzp stage 3 kit with 60lbs injectors with zzp coils as well
03-18-2019, 08:23 AM
#2
Hopefully you didn't get into the boost much when you had 87 octane in the tank. I would run the car and then pull the spark plugs and compare them to cylinder 2. With it being specific to cylinder 2 you essentially have 3 possibilities for what is wrong, fuel, spark, or low on compression.
03-18-2019, 09:40 AM
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I'd rule out the fuel as it is a single cylinder misfire, but not rule out that the injector could be fubard. First step, look at the plugs and try swapping cylinder 3 with cylinder 2 (spark plug only). If the misfire moves you need spark plugs, if it doesnt try moving the coil pack to a different cylinder. If it doesn't move it's time for a compression test and leak down.
03-18-2019, 03:18 PM
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myself, id go straight for a compression test, but thats just me. do a compression test and then swap 2 and 3 plug around and see what happens, if the problem doesnt move to 3 then swap 2 and 3 coil, if the problem still doesnt move you can try swapping injectors around.
03-19-2019, 02:00 AM
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Po302 misfire gone
Hopefully you didn't get into the boost much when you had 87 octane in the tank. I would run the car and then pull the spark plugs and compare them to cylinder 2. With it being specific to cylinder 2 you essentially have 3 possibilities for what is wrong, fuel, spark, or low on compression.
I'd rule out the fuel as it is a single cylinder misfire, but not rule out that the injector could be fubard. First step, look at the plugs and try swapping cylinder 3 with cylinder 2 (spark plug only). If the misfire moves you need spark plugs, if it doesnt try moving the coil pack to a different cylinder. If it doesn't move it's time for a compression test and leak down.
myself, id go straight for a compression test, but thats just me. do a compression test and then swap 2 and 3 plug around and see what happens, if the problem doesnt move to 3 then swap 2 and 3 coil, if the problem still doesnt move you can try swapping injectors around.
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