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Bought an 04 civic Si 330,000 km. Recent timing belt and water pump replacement as well as alternator. On the way back from a road trip, over 400 km, car develops a misfire
(random). Turns out to be a burned exhaust valve in cylinder 4. Pull head replace valves and valve stem seals, gaskets and head bolts. Put back together, misfire cylinder 4. Check
compression 170 good. Spark is good. All fuel injectors tick exactly the same. Swap injectors 4 and 1. Still misfire cylinder 4. Last thing I can think of is EGR valve, which I cannot
remove due to seized and rounded nuts. I'm hoping to crowd source some ideas here. Thank you for reading.
Thanks for the reply. I only have a handheld OBD2 reader, gives me P0304. Not sure the device I need to get freeze frame data. As soon as you start it you can tell its running rough. I took the head off without removing the intake manifold. I'm going to buy a nut splitter and get that egr off and look for clogged passage ways. It sputters when throttle applied and puffs exhaust. Also I'm missing one nut on the exhaust manifold and exhaust leaks from there a little.
So all cylinders had a compression around the 170 psi mark. I checked spark in cylinder 4 and was good. I swapped cylinder 4 and 1 injectors. Misfire stayed on cylinder 4. I set all the exhaust valves at .011 lash. I checked continuity of the egr valve, seemed to be good. Could use some direction on how to use my multi meter to check position sensor, like which pins and what setting on meter. Do I have to remove to intake manifold to examine the egr distribution plate?
Plugs and coil packs are brand new. I could double check gaps and try moving plugs around just in case one fouled somehow. Seems like everything is there for ignition ( fuel spark and compression ) . I reset the ecu by pulling the fuse for 10 seconds. I don't know if this is an air flow problem or a computer problem.
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Re: 04 civic si misfire mystery
P0304 code no matter what coil, plug or injector is in cylinder 4.
I'd Fix EGR problems FIRST, because EGR could cause the miss code.
Intake passages probably still need to be cleaned out to get rid of the miss code, if it is EGR related. FF data could reveal more about that.
There's a couple more steps you could take to confirm prior to pulling the intake to get st those passages though.
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
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From: Midwest. Aiming about mid-chest
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Re: 04 civic si misfire mystery
EGR valve Pintle looks like it's closed now.
If you connect its wiring right now Does the voltage reading reflect that?
You COULD cut a chunk of cereal box thin cardboard into the shape of the gasket (no holes for the passages though), place it under between the EGR valve and its mount to block the passages, bolt the valve on (just tight enough to cinch the cardboard so it doesn't leak) and see if your miss is gone
(except you took the entire housing off the end of the head?)
Blocked off EGR ports with cardboard gasket, car will not start. Put EGR on with new regular gasket, car will not start. Guess Im going to have to pay someone to figure this **** out. Thank you ezone for trying to help me.
Everything seems to be plugged in. Pretty sure I put back on everything I took off, including the ground wire. First time it didnt start i checked for codes and had a p0118 which is ECT. Cleared it but still wouldnt start, code never came back. Its been an hour since it wouldn't start so just tried again now, almost started but wont quite turn over.
If you think a good mechanic is expensive, try hiring a bad one
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From: Midwest. Aiming about mid-chest
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Re: 04 civic si misfire mystery
Originally Posted by jikemohnson
What does coolant temp have to do with ignition of engine?
It has everything to do with fuel delivery. False cold reading causes a ton of extra fuel to be injected.
Also.....a cold start followed by moving the car 15 feet and shutting it off (or any similar short run time for whatever reasons) leads to flooding too. Gotta keep it running and driving long enough to warm up and burn the soot off the spark plugs before you shut it off.
Deflood: Dry out the plugs, clean if necessary with brake cleaner or carb/throttle cleaner.
Dry out the cylinders if possible (crank with plugs out, blow compressed air in, etc.)
Might even need to re-oil the cylinders so the rings can seal and regain the lost compression......this is a common need.....don't overdo the oil though, you can hydrolock it if you add too much and forget to spin it over to get rid of the excess oil.
The Oil you dump in and the fuel that's already in there can foul the plugs repeatedly.....keep cleaning and drying until the dang thing will run on its own
Hold the gas pedal to the floor during cranking OR disable fuel (pump or injectors) until the fuel already in the engine can be burned off
Ok, I've put in a new coolant temp sensor. I put a very little amount of oil in each cylinder. I cleaned each spark plug. Engine will not start. I tried 3 times, pull plugs clean reinstall and try. Each time wont start at all. I thought leaving it for a week would allow it to dry out. Cant figure out why it wont fire.
Update....finally got somebody to help me turn the key while I visually confirm spark on each plug. Turns out 2 plugs were not sparking even tho I clean them and checked continuity with a multi meter. Put 2 new plugs in and it started, but popped and hissed and within 15 seconds stalled out. A bunch of smoke was coming out of the front on the engine, could not see where but I'm hoping its just fluids burning off the exhaust. New plugs were kinda black when i pulled them, cleaned all plugs again and engine started again but ran rough instantly and stalled quicker this time. Cleaned plugs again but wouldn't start again.
Brand new plug ran for 15 seconds.
If you think a good mechanic is expensive, try hiring a bad one
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From: Midwest. Aiming about mid-chest
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Re: 04 civic si misfire mystery
If the plugs are getting fouled with too much fuel they would be wet when you pull one out. If that's the case then starting fluid can't help, that's just more fuel on top of too much already.
Also it looks like the gasket on your plug wasn't squashed. Plug was not installed tight enough.
Finally took my Civic to a Honda dealership service department because I figured Honda of all people would be able to figure their own vehicle out. So far no. Timing is correct, compression is good, spark is good. They say the plugs are dripping with fuel. They don't know why. If they don't know then who would know?
If you think a good mechanic is expensive, try hiring a bad one
Joined: Dec 2011
Posts: 32,017
Likes: 256
From: Midwest. Aiming about mid-chest
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Re: 04 civic si misfire mystery
They don't know why. If they don't know then who would know?
Sadly, not all who work on cars have problem solving skills.
Most dealers try to keep at least one smart tech in the shop, but....if they don't have anyone fitting that description and/or you got a rookie parts changer assigned to your car, you lose.
04 civic si misfire mystery 
