wright

Ok,

I am looking to see if any knows if there is a common issue with a random misfire in the 04 civics’.


I am trying to fix the misfire issue for my mother in-law, but it seems that everything that I have tried has not corrected the issue. Everything started a few weeks ago with the bank one O2 sensor. We received a new O2 from Honda and that was replaced. Now the car has been getting misfire codes.

The weird thing is that most of the time it seems to be just cylinder number 3, but every other time that the light comes on it becomes a random misfire with 1,2,3. If I recall correctly cylinder number 4 has not shown up with a misfire code.

Trouble shooting the issue:
I replaced the spark plugs.
Swapped number two and three coil packs (number three still shows a misfire. I assume that it is not a coil pack issue).
Put a bottle of Lucas Oil fuel injector cleaner with a full tank of 93 (did this yesterday)

While driving the car into work today the check engine light came on again showing that cylinders 1,2,3 have a misfire.

So, I guess my question is there anything else to look at other than removing the injectors to clean them by hand? The car has 130k on it and the timing belt ect was done at either 90 or 100k.


Thank you,

jdm jim

find a shop that can do a BG fuel induction cleaning on it. i'd do that first.

StreetEvo

Is there any oils in the spark plug tubes or on the plug boots?

wright

^^^^^ Nope no oil in the spark plug tube everything looks clean for the most part.

At this point I am trying to see if there is a common issue with this generation. I think at last resort I will pull the injectors out to see what they look like.

Fabrik8

Because three cylinders are showing the same issue, I'd assume it is something affecting multiple cylinders and not something like a coil pack or injector issue. Injectors don't fail all at once, coil packs don't fail all at once, etc.

A likely suspect is an engine position sensor like the crank angle sensor or cam sensor, or the O2 sensor, any of which would usually generate a code for the bad sensor but not always. Sometimes a partially failed position sensor will drop a pulse here and there, but not for long enough to do anything but confuse the hell out of the ECU. A position sensor that drops a lot of pulses will get detected by the ECU and will trigger a CEL.

It's also possible that there is a problem with the engine harness, and that the injector or coil pack isn't getting power or signal like it should. The number 4 cylinder might not be affected because of how the harness is made, and it's fully possible that one wire on part of the harness feeds cylinders 1, 2, 3, and another wire feeds cylinder 4.


I guess I should also add that it's also possible to have a TPS, MAP, or intake air temp sensor problem, but usually those will result in noticeable drivability problems instead of only random misfire codes.

In all honesty this could be a bitch to track down. An OBD2 scanner would help, but only if it does real time scanning and/or datalogging, and only if you can actually capture the misfire event and the sensor data surrounding that event. But, it may be simpler than that; you might see some sensor signal that is out of range all the time, but that would be lucky.

I would check the voltage on the 12V supply on all of the coil packs and all of the injectors (engine doesn't need to be running, and it's safer if it isn't while you check the coil packs), and also check for any differences in voltage between the various grounds around the engine.

I'm not trying to scare you with all of this, it's just that problems like this are a lot nicer to diagnose if the problem is consistent. Because it's really hard to diagnose something that only shows up once in a while. So I hope it's something easier than that (like a voltage problem).




Good luck, use your head and think carefully about what you're doing and what you're seeing.