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2014 Civic P0303 Code before and after engine replacement

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Sep 6, 2022, 7:01 PM

Post #1 of 3 (469 views)
2014 Civic P0303 Code before and after engine replacement Sign In

Car Details: 2014 Honda Civic LX, 1.8L, 4 Cyl, 180k miles

Question: What potential causes are there of a recurring cylinder misfire after replacing the original engine with a low mileage used engine?


Issue first occurred when driving downhill on the highway. Check engine light and the following warnings came on at the same time: Check TPMS, Check Emissions System, Hill Start Assist, Check VSA, Check Power Steering Assist. Took it to AutoZone and got a P0303 code reading. Car was off overnight and the next day check engine and all warnings had cleared and car drove normally for months.

Issue next occurred when stopping at stop sign from low speed. Check engine and the same set of warnings came on. The car began rough idling, had slow acceleration, and power loss.

The code it read was again P0303. A mechanic replaced plugs and coils and it passed test drive. Drove the car away and 20 miles down the road the same warnings and symptoms began again, so took it back. Mechanic couldn't diagnose, so took it to dealership who diagnosed as the following: likely bent intake valve due to 100% leak down of 3rd cylinder and air coming out of intake box.

Recommendation was replace engine immediately, rather than find cause and rebuild/repair, so I had the engine replaced with a used engine with 44k miles and a 3 year parts/labor warranty. After driving normally for over 50 miles the same warnings and symptoms occurred once again. After leaving the car off for 2 hours, the warnings remained but the car drove normally for another hour.

Hammer Time
Ultimate Carjunky / Moderator
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Sep 6, 2022, 7:15 PM

Post #2 of 3 (462 views)
Re: 2014 Civic P0303 Code before and after engine replacement Sign In

You most likely have a wiring problem in the harness. Could be a pin connection at one of the plugs or a problem with the wires themselves.

With the engine idling start manipulating the wiring around while listening for a change in the engine to indicate you hit the spot.


We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.

(This post was edited by Hammer Time on Sep 6, 2022, 7:16 PM)

Tom Greenleaf
Ultimate Carjunky / Moderator
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Sep 6, 2022, 7:38 PM

Post #3 of 3 (455 views)
Re: 2014 Civic P0303 Code before and after engine replacement Sign In

 That didn't make my day to read that! Are you just maybe dealing with rodent damage to wires? They leave you see evidence.
It's a far reach from warnings about tire pressure and needing a whole engine (done) and same issues.

BTW if test that blew air back thru intake done properly for cyl. #3 (any) like that it's pretty damning as you were told sorry they didn't want to fix that - was probably a crack in an intake valve?? Never know now,



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