Rep Power: 0

I have Civic 2005 LX had it since it was new and had no issues with it, except around 120,000 miles I had exhaust leak into coolant so I replaced head gasket and did timing belt and all the other stuff with it ( water pump, other belts, etc.... ) right now I have ~150,000 on it and every now and then I get P302 code I can feel it misfire for couple seconds (maybe 10) when I start the car but then it goes away a drives normally, no issues at higher RPM at all. This happens if the its cold start or warm, but does not happen all the time. I have tried leak down test on all cylinders and and they are about the same ~15%, Compression test 1- 140, 2- 135, 3- 140, 4- 145, these test are on cold engine. Replaced spark plugs, change ignition coils around, switch fuel injector from cylinder 2 to cylinder 3. but it always comes back as Cylinder 2. Spark plugs seems to have oil residue on them from cylinder 1-3, but cylinder 4 is clean. there is no white or blue smoke coming out of exhaust. could this be failing head gasket or valve seals ? or something else ?

 
Rep Power: 118

If you mean p0320 then I would suspect your crankshaft sensor is going bad and or connector is contaminated .

Maybe start with unplugging it and spraying 1/2 can electrical contact cleaner on it and the connector.

If it’s p0302 then I would check the ground connectors for the engine harness (on the water passage by thermostat )

 
Rep Power: 0

It is P0302 and all ground contacts are good, when the car is running and I plug one coil at the time there is always change in the engine.

 
Rep Power: 0

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If you mean P0302, this is a misfire on cylinder #2.
The most likely cause is ignition or fuel. Check the Honda manual for the correct troubleshooting procedure.
I had a similar code on my '02 Civic LX (200k miles). The engine also had a rough idle, poor gas mileage, hard starting. This was all caused by a bad fuel injector.
I replaced all 4 fuel injectors with rebuilt OEM units from Amazon ($38). The engine now runs GREAT again. No more codes, gas mileage back to 34 MPGs, nice SMOOTH idle! :-)

 
Rep Power: 0

The thing is I tried to switch injectors around to see if anything changes but I still get misfire on cylinder 2 and I know I have put injector from cylinder 2 to cylinder 3. But I only get misfire on cylinder 2 and only at start. Once it’s starts going everything runs great. Almost seems like it’s get better compression at higher rpm and on start it just take few second before it runs normal ?

 
Rep Power: 0

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Did you get a misfire DTC code on Cyl # ___, then clear the code, move the injector, run the engine and get the same code on the same cylinder?