Rep Power: 0

Hi all, new here and new to 7th gen Civics (I do have a 1981 Civic wagon that runs great though!)

I bought a 2002 Civic sedan recently and it's throwing a bunch of codes related to cylinder 4. Don't have the specific codes written down, but ithey were all related to cylinder 4 operation...fuel problem, spark problem, misfire, etc. The car vibrates at idle, can hear irregular exhaust sound. The car runs and drives mostly fine, but you can tell its a little down on power at low speeds. Runs great above maybe 2500 rpm, sometimes the check engine light will even turn off while driving until I return to idle, then it'll come back on. Car has 189k miles. I have NOT done a compression or leakdown test just yet or checked valve clearances yet. Tonight I started it up with the airbox off and removed the injector connector on cylinder 4. No change. Removed the coilpack. No change. However doing this on any other cylinder will basically kill the engine.

I'm sure a compression test will tell me more immediately, but I'm confused why the engine is able to start and run fine no problem with what seems to be an unresponsive cylinder, yet pulling the coilpack or injector connection on any other cylinder kills it. I'd think it just wouldn't even start at all if it's that finnicky with the other "good" cylinders. Is this most likely a sign of a dead cylinder, or do you think something else is up?

I don't have time to mess with the car until this weekend, any pointers are much appreciated!

 
Rep Power: 99

I believe the engine can run with one bad cylinder, but it will be very imbalanced (explaining your engine shaking at idle). For sure do a compression test to get some direction. If that tests ok, then try swapping the coil for another and see if the problem follows the coil.

 
Rep Power: 0

I actually bought a new coil tonight and performed the test with it. No change with the coil removed so I think it's unrelated to the coil itself, however that doesn't rule out a situation where the coil isn't receiving voltage at all...lots to consider here.

 
Rep Power: 0

Well, I pulled the fuel rail off last night to look at everything. Measured the injector resistance and got just over 15 ohms on all four. Did a dry compression test on cylinder 4 and got a whopping 25 PSI. Is cylinder four known for being a failure point on these motors? Think it’s head or ring related most likely? Hoping head…

Whats the next step? Leakdown test? Wet compression test? This sucks…

 
Rep Power: 99

Yeah, I'd say you're on the right track...

Wet compression test will help determine if the rings are bad, but leak down test should pinpoint the source of the low compression.

 
Rep Power: 0

I did a compression test and got the following readings on cylinders 1-4: 177, 180, 180, 20.

Looking into the spark plug hole, i saw a light spot on the piston and assumed it was a mark from bending a valve. Took the head off today and there was an extremely burnt exhaust valve on cylinder 4. Going to replace both exhaust valves and put it back together. Glad it ended up being head related...still a pain!