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Hi all, my car is 2001 Civic LX 186K miles. For about last few weeks I am getting multiple cylinder misfires. I cleared them 3-4 times to see if they return but codes usually come back after 2-3 days of regular driving. No performance issues once car is warm. only once 2 weeks ago, car wont start and it took good 5 minutes of cranking attempts to get it start. That was done with the help of jump from my running van. However when it started, it felt like running without fuel (i know it doesnt make sense) for 4 seconds before it actually fired up. Didnt have any starting issue after that but codes still came back after clearing. I swapped 1-3 and 2-4 ignition coils. Cylinder 4 misfire always comes back. Spark plugs were replaced (NGK) 20K miles ago when I did a head job and replaced headgasket too. Most recent codes indicated 1,3 and 4 misfire. I cleared them last night. The data below comes from 2-4 misfire.

Following in Freez frame data if it helps
DTCFRZ P0304
Fuelsys1 OL
Fuelsys2 NA
LOAD PCT % 54.5
ETC-F 19
SHRTFT1 0.0%
LONGFT1 -14.8%
MAP(In Hg) 16.2
RPM 1768/min
VSS 0 mph
IAT 16F
TP10.6%

Other problem that might or might not be related is a bubling from right side of engine, close to engine coolant temp sensor. its hard to explain the location but I have a video at
My worst nightmare would be a bad gasket but I want to check things systematically before reaching conclusions.

 
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not sure about the mis fire, but it would appear from the video that there is coolant leaking out around the sensor, just remove it and re seal it

 
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Video: I see a straight line of bubbling....Looks like the neck is leaking, where it bolts to the head? Lack of gasket/sealant?

FF looks like a cold startup.
Dead miss on cold startup, or is it missing on all cylinders on cold start?

Have you rechecked for coolant intrusion in that cylinder (or any) overnight?

Valve adjustment?

 
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Yes, bubbling is along that line. i guess i will have to change if a gasket is there. I will do that with my valve cover gasket change.

I would say it is probably missing one or more cylinders on cold start. We have been having a brutal winter this season in Boston. Cant wait to start my next job in texas in few months. If i put it to drive immediately after cold start, engine would turn off and then take a lot of cranking to start again. therefore, i immediately give gas after start for 2 min, until temp guage starts to move from its resting position. then I drive and then it is ok. Today i made a video of exhaust immediately after cold start. I have never heard a miss from exhaust but something sounds like a pop after every 3-8 puffs. I will post it soon.

I dont know how to check for coolant intrusion in cylinders. I guess it would mean to take out spark plugs and to somehow look for coolant inside after car has been sitting overnight. I do plan to open spark plugs and look at them once weather is better and I am off from work.

Valve adjustment was done almost 1.5 year, 20K miles ago when did a head job.

Thanks Ezone, you have always been very helpful.

 
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following is a video of exhaust immediately after cold start in morning . temp around 18F. see how popping sound decreases.

 
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I think the popping is probably random misfires.

 
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what should I do about it. Is it electrical issue or fuel problem. I know compression problem cant be intermittent. How should I check for coolant in cylinders after an overnight?

 
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pull your plugs,

what color are they?

take pictures of each plug and post here

 
Rep Power: 518

Fix it.



Hell if I know.
All I know is you have a misfire code.



Yes, it can.
It certainly isn't the norm, but it sure can.
If it fires up and runs with a dead cylinder, then I might suspect something like coolant.. I might shut it off while it is still missing, and inspect the plugs. Find if one is soaking wet, and figure out what the liquid really is (taste it).


Or
Let it sit overnight....you know, set it up for a time you KNOW it will miss if you start it.
Pull the plugs, look in the cylinders. Use a strong light.


Stand in front of the engine after you get the plugs out.
Have someone crank the engine over, watch the spark plug tubes for anything to come out.
If you get shot in the eye with antifreeze, it's safe to assume that's a problem.

No really, stand off to the side, not directly in front of it. Do watch, just don't get hit.

But that's only for a dead miss.
If you fire it up and it only misses randomly and occasionally (as the exhaust video sounded like), then I'd probably look for a completely different problem instead (likely ignition).
^What he said.

Your occasional pop from the exhaust in the video, is that the worst it runs when it sets the misfire code? Or does it run a lot worse than that?

 
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Since the weather is better is now, I was able to open the spark plugs and here is the photo. Back in start of march temperature was running in 10-25s F and I was getting above issues. Now temperature is in 35-60s. Relatively good news is that I have not got misfire triggered check Engine light since start of march. Its been almost 50 days. In between I have put 2500 miles on car. I changed valve cover gasket yesterday and that's when I took out spark plugs and took a photo.

 
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Doesn't look like they were torqued again after installation, as per all spark plugs. Lot of carbon up those threads and past the sealing washer. Carbon up that high can arc under the right circumstances... plug swap ( I suggest the Denso OEM plugs, but buy from Amazon vs. your dealer -- they are eye-wateringly-pricey. 100K plugs though).

The OE Densos in my '04 EX were the showroom plugs -- and they also misfired esp cold, until I swapped them for new.

Compression-related misfire is indeed rare -- so rare, I've never heard of it, at least on an engine that actually ran after it happened (knock so bad it detonates the the ring land apart, sure that's a candidate ). Lots wrong with the piston/ring/cyl/valve seal for compression to be so low the TDC mixture's too lean to fire a correct injector pulse.

 
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all those plugs look pretty normal to me

 
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I agree with both of these statements.

The burn looks normal on the electrodes BUT they have the appearance of being run loose enough to leak combustion past the threads.