tamouq

My 2004 Civic LX coupe has been throwing misfire codes for a few months now. It also idles incredibly rough. I can unplug the coil and/or the injector plug on cylinders 2 and 4 and it doesn't make it idle any worse. I started at the spark plugs and coils and replaced them all, no change. New air filter, no change. I pulled all the injectors and cleaned them the best I could and rearranged them and still had 2 and 4 misfiring when idling. I should note that once you give it some gas it smooths out. I sprayed throttle body cleaner into the throttle body and cleaned that the best I could without removing the entire thing. Finally I moved onto a compression test and I get 210, 210, 210, 110. Looking around on here it looks like the consensus is around 135 is normal. 210 is obviously way too high. I replaced the timing belt last year when I got this car as I believed it was on the original one and it had around 165k on it, 185k now. Could it have slipped? Is it a burnt valve? Not sure where to go from here. Any suggestions would be appreciated.

ezone

210 is normal, 110 is your problem for cylinder #4.
I can't tell from here why #2 is misfiring though.
Got freeze frame data to post, and note the specific fault code associated with that data set?
Mileage?

Check valve clearances, then if compression test STILL shows that #4 cylinder extremely low, do a cylinder leakdown test to determine where the leakage (loss of compression) is going.

Still need more info on #2 miss though.

tamouq

I had a friend that checked the codes and he said that all four cylinders had the misfire code tripped. He reset them all and 2 and 4 instantly came back. We would unplug those 2 coils and/or injectors and would notice no difference, still running bad. I don't remember the codes exactly, P0301 (1-4)? I thought that for the compression that seemed way too high based on what others were saying in some older threads but that's good to know. We are going to check the spark plugs again because we have a weird feeling about them and then also do a leakdown test. Thank you for the response!

Edit: Forgot to mention that the car and motor has 184k miles on it. Burns oil not at a ridiculous rate but enough to where it needs to be topped off here or there between changes.

ezone

When I do a compression test on one of these, I totally expect 180 PSI or higher using my tools, my methods, and a fully charged battery (to keep cranking RPM up).
210 is not out of line IMO.

If #2 misses but has good compression then you could be looking at fuel or spark problems, but #4 does have a compression problem that does need attention.

You could swap coil, plug, and injector from #2 to each of the other cylinders (example swap coils between 2 and 1, plugs between 2 and 3, then if miss is still present on #2 you could swap injectors between #2 and another cylinder) whichever cylinder the miss moves to would indicate the pad part.
If miss stays on #2 after all that then it's a mechanical problem

I asked about freeze frame data to try to see if it's not an EGR distribution passage clog issue.

tamouq

I have tried swapping coils and injectors from #3 to #4 and saw no change, still cylinder 2 and 4. I mentioned spark plugs again because they did look alright and in order for the most part but we did not swap them around and that's what I'm going to start with tomorrow. My friend with the computer is out of town for a few days so I can't get that data now but when he did have it hooked up he said everything looked fine besides the obvious misfires.

ezone

My thinking was to stay away from swapping any parts from #2 to #4 because #4 already has low compression and misses.

I was thinking 1 and 3 don't have misfires so swap the various items from #2 to cylinders 1 and 3.

Yea, by all means check plugs for anything obvious and swaparoo if necessary.
OTOH if you pull #2 plug out and say "oh hell" then you probably found the problem LOL

NDNV

Recommend you stick with the OEM NGK Platinum spark plugs. No Bosch.

tamouq

I've tried just about every combination of plug, coil, injector, etc. to no avail. I will note that after reassembling everything back to normal today that when I unplugged coil and/or injector #2 it did make the engine bog down a bit like the two good cylinders would do. It wasn't a hugely significant difference but noticeable. Maybe me cleaning the injectors and plugs solved that cylinders issue?

I moved onto a leak down test. I found TDC with a screwdriver and turning the crankshaft. I applied around 90 psi of pressure to cylinder 4 while the other cylinders had their plugs in. Pulled off the radiator cap and saw no bubbles. Oil fill hole and dipstick had the slightest tiniest draft coming out of it, barely detectable. The throttle body did have some air pressure building behind it and when opened had a slight draft escaping, not very bad. The exhaust however did have a significant amount of air pouring out of it. I wasn't sure exactly if the valves were closed because both were leaking so I spun the motor over one revolution back to TDC and tested again. When I applied pressure both times my ratchet did not budge so I assume the piston stayed up. Again I had the same results across the board.

I guess this says I should try a valve adjustment? Just to reiterate the compression was 210 210 210 110 (1-4). Is that the next logical step? Another question I have is, if the valves were the issue to the compression being low, is that really the problem with the misfire? I have verified spark and fuel presence many times in it and to me, 110 compression should still allow the motor to run okay. For how violent it runs at idle you would think that there was just no spark or fuel yet there is and there is compression it's just low. Thoughts? Thank you ezone and NDNV for the help.

ezone

"TDC compression" occurs on every other crankshaft revolution, so at least one of the attempts should have been in the correct spot.
1 and 4 are companion cylinders, their pistons are always in the same positions in the cylinders but opposite points of the 4 stroke cycle.
You could screw the compression tester whip into #1 and feel when it whiffs a puff of air out indicating #1 compression stroke (therefore you know it's about to be on TDC) and #4 is on overlap at that time. Another 360 on the crank and 4 will be on TDC, #1 will be on overlap.

Yes, check valve clearances and adjust if necessary. Tight valves can cause low compression and leakage, and tight valves will burn if ignored too long.
You can even have good looking compression yet have valves with clearances too tight.

At the very least, during the leakdown check I may have yanked the valve cover off and checked that the rockers on the cylinder being tested have SOME amount of free play (indicating the valves are not being held open by incorrect adjustment, although this is not actually measuring for correct adjustment, only verifying the valves are closed for the test.).


You have low compression.
Hondas valves are manually adjusted.
Valve clearance checks are the next step.
Period.


Do you really want to pull the cylinder head off just to find out the valves were too tight and you didn't really need to pull the head off?

If the valves really are shot and you have to pull the head off, don't you want to know what caused the valves to burn?

tamouq

I guess my question is even if the valves are too tight or burned shouldn't the cylinder at least be firing? I have verified for sure that it has spark and fuel. It acts like a coil pack is unplugged or an injector is not firing. My experience is with bigger motors but shouldn't it still fire even with 110 compression? I do plan on doing valve adjustments the symptoms I'm getting don't make sense in my mind.

ezone

Depends.

If 210 is the norm measured in this engine then 110 is a huge freekin problem.Which cylinder are you referring to?