03 Honda Civic LX manual P0303 code Hi! I’m new to here so I’m not sure if this is the right spot to post. So a few months back (Feb 15th) I have a P0303 code pop up. Had it checked to find a cylinder 3 misfire. Put new spark plugs and coils in it and it was good to go. Now four months later (July 5th) the check engine light blinked twice back on and shut off under the P0303 again. I know it can’t be my spark plugs and coils again?! Replaced the spark plugs again just to be safe. it’s having a rough idle.. I took it to get diagnosed and they told me no issue found. But you can hear it from my tailpipe.. apparently they didn’t hear it until after I picked the car up. I had them do a compression test and cylinder 1-3 were at 170. Cylinder 4 at 150. Shop said I needed a new intake 02 sensor and a induction clean. $700 later my cars running worse, the 4th cylinder dropped to 120 and the check engine light is staying on now. Now it’s hesitating to turn over. Never did that before.. The car has 244k on it, mainly highway miles. I’m at a total loss of how to fix this misfire.. I had gas getting into my oil to where when you opened my oil cap it was so strong. Burnt bad valve? Fuel injectors? Anyone have any experience with this problem already? I haven’t popped anymore codes besides the P0303. Until the induction clean, now I had a code for my fuel being to rich. Someone help 😩 |
Re: 03 Honda Civic LX manual P0303 code
Originally Posted by Jess17
(Post 4778577)
Hi! I’m new to here so I’m not sure if this is the right spot to post. So a few months back (Feb 15th) I have a P0303 code pop up. Had it checked to find a cylinder 3 misfire. Put new spark plugs and coils in it and it was good to go. Now four months later (July 5th) the check engine light blinked twice back on and shut off under the P0303 again. I know it can’t be my spark plugs and coils again?! Replaced the spark plugs again just to be safe. it’s having a rough idle.. I took it to get diagnosed and they told me no issue found. But you can hear it from my tailpipe.. apparently they didn’t hear it until after I picked the car up. I had them do a compression test and cylinder 1-3 were at 170. Cylinder 4 at 150. Shop said I needed a new intake 02 sensor and a induction clean. $700 later my cars running worse, the 4th cylinder dropped to 120 and the check engine light is staying on now. Now it’s hesitating to turn over. Never did that before.. The car has 244k on it, mainly highway miles. I’m at a total loss of how to fix this misfire.. I had gas getting into my oil to where when you opened my oil cap it was so strong. Burnt bad valve? Fuel injectors? Anyone have any experience with this problem already? I haven’t popped anymore codes besides the P0303. Until the induction clean, now I had a code for my fuel being to rich. Someone help 😩 just unplugged all the fuel injectors while leaving it running, all made it run a lot worse so I’m assuming all injectors are ok |
Re: 03 Honda Civic LX manual P0303 code Misfire on a single cylinder (cylinder 3 in your case) will make the car's idle sound like a galloping horse. Is your check engine light flashing or is it steady on? I see you already replaced plugs and coils, so kinda ruled that out. You can swap around the coils to see if the code follows the coil (e.g. swap cyl 2 and 3 coils and you start popping a P0302 instead of P0303). any signs of any frayed wiring in the engine bay? Also, moved to right sub-forum. 7thgen, not 6th edit: that lower compression on cyl 4 and drop down to 120psi is disconcerting, btw. I'd honestly be expecting that the misfire would be in cyl 4 with that kind of info. You may be in for a head gasket change free-er things you can check, make sure plugs are gapped properly. .044" is the spec, IIRC |
Re: 03 Honda Civic LX manual P0303 code
Originally Posted by Jess17
(Post 4778577)
I needed a new intake 02 sensor and a induction clean.
Originally Posted by Jess17
(Post 4778577)
The car has 244k on it, mainly highway miles. I’m at a total loss of how to fix this misfire.. I had gas getting into my oil to where when you opened my oil cap it was so strong. Burnt bad valve? Fuel injectors? Anyone have any experience with this problem already? I haven’t popped anymore codes besides the P0303. Until the induction clean, now I had a code for my fuel being to rich. Someone help 😩 |
Re: 03 Honda Civic LX manual P0303 code
Originally Posted by xRiCeBoYx
(Post 4778580)
wtf.. I think they got you there. If you needed an O2 sensor, you'd be throwing a code for it. As far as what an intake O2 sensor is.. idk. Only sensors on the intake stream of a 2001-2005 civic are intake air temp and manifold air pressure sensors. O2 sensors are on the exhaust pipe, one upstream of the catalytic converter to measure air/fuel ratio and one downstream to monitor catalytic converter health. If they replaced the upstream O2 sensor with a non-oem one, these engines/ECUs don't play nice with aftermarket/universal sensors. Induction clean? Did they just replace the filter and wipe it down with a rag? Fuel in the oil system... could be leakage past the piston rings. Leakdown test will be able to tell you if you have any leakage there. idk if someone else has ideas of how to tell without coughing up $200 for a leakdown test to be done. At the moment, can't think of any other source of fuel to oil leakage.. Valve seals maybe? |
Re: 03 Honda Civic LX manual P0303 code
Originally Posted by xRiCeBoYx
(Post 4778579)
Misfire on a single cylinder (cylinder 3 in your case) will make the car's idle sound like a galloping horse. Is your check engine light flashing or is it steady on? I see you already replaced plugs and coils, so kinda ruled that out. You can swap around the coils to see if the code follows the coil (e.g. swap cyl 2 and 3 coils and you start popping a P0302 instead of P0303). any signs of any frayed wiring in the engine bay? Also, moved to right sub-forum. 7thgen, not 6th edit: that lower compression on cyl 4 and drop down to 120psi is disconcerting, btw. I'd honestly be expecting that the misfire would be in cyl 4 with that kind of info. You may be in for a head gasket change free-er things you can check, make sure plugs are gapped properly. .044" is the spec, IIRC thank you I wasn’t sure what gen it was! Lol the check engine light is steadily on now. No flashing. I haven’t checked to see if any wiring is frayed I’ll look into that! Spark plugs I bought pre gapped but I double checked them and they were on the money. And I was wondering if maybe a head gasket but no smoke showing signs of it. |
Re: 03 Honda Civic LX manual P0303 code head gasket failure might not always show smoke. last time mine blew, didn't smoke at all, but my oil was definitely chocolate milkshake |
Re: 03 Honda Civic LX manual P0303 code
Originally Posted by xRiCeBoYx
(Post 4778585)
head gasket failure might not always show smoke. last time mine blew, didn't smoke at all, but my oil was definitely chocolate milkshake |
Re: 03 Honda Civic LX manual P0303 code tbh, last time my head gasket blew on my 2002, zero codes, car ran fine-ish with the occasional temp rising. Was losing coolant is the only thing I noticed. Until the gasket blew blew and there was active coolant leakage from the backside of the block If you wanna see what blown headgasket oil looks like, click the "RIP Azumi" link in my signature. |
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