Random cylinder misfire
 

I have a 2008 Honda civic 1.8L. It has no mods but has been throwing codes for a little bit now and I can't figure it out. It comes up with a check engine code for cylinder 1, 2, 3, and 4 misfire and a random cylinder misfire. This will only happen when on the freeway when cruising at a reletively constant speed with low throttle position after 30 minutes or so on the freeway. (It has never happened while city driving.) Very often when these codes come up it will put the car into limp mode but not always. I have replaced the downstream o2 sesor and all of the spark plugs with the recomended lazer iridium plugs in attempt to fix the problem but no luck. I have read all other forums on the issue and there seems to be no consensus. Things like the crank positions sensor, cool packs, maf, o2 sensors have been recommended on these forums but I hate to just aimlessly start replacing sensors. Especially when there is no code thrown for any sensor malfunction. I find it odd that the car will only throw the misfire code but not a code telling me why it is misfiring. Any help is appreciated

Re: Random cylinder misfire
 

Since it's an intermittent issue you'll need to test it while the issue is occuring. If you don't already have one you can purchase an OBD2 data scanner (one that includes Honda) to check freeze frame and live date. Data can be captured while driving/ issue occurs.

Other than using a data scanner you can try a power balance (drop) test while engine is idling.

Re: Random cylinder misfire
 

so when it does happen, while looking at the freeze frame what should I be looking for.

Re: Random cylinder misfire
 

Do you ever FEEL it running poorly? Losing power, vibrating, etc?


Freeze Frame data is simply a set of data that is stored at the time a fault code sets. It can give us an idea of what the conditions were when it set the code. A decent scanner can display this data and it shows things like vehicle speed, RPM, coolant temperature, fuel trims, and more.

Re: Random cylinder misfire
 

As Ezone mentioned. Both long and short term fuel trims + fuel pressure for possible lean issue. o2 voltage, MAF readings (if available).

I forgot to mention yesterday to also inpsect for vacuum leaks

Re: Random cylinder misfire
 

No, not at all. Unless the car puts itself in manufacture control of course(LIMP MODE). But if it doesn't put itself into manufacturer control, I don't even notice a difference except for the CEL.

Now for vacume leaks I suppose this could be the issue however, I have read that I would be seeing large positive numbers for fuel trim at idle. When looking at live readings this is not the case.

so I will be commuting a long distance starting again tomarrow so it should only take a day or two to get the freeze frame data and see if we get anything from that. I suppose I'll just report back.

Re: Random cylinder misfire
 

So i have new info on the car. I got the freezeframe after the code was thrown it is as fallows
Freeze frame 0 information:
------------------
Engine Load = 78.431 %
Engine Coolant Temperature = 190.4 °F
Intake Manifold Pressure = 11.603 psi
Engine RPM = 2,601 rpm
Speed (OBD) = 79.536 mph
Intake Air Temperature = 89.6 °F
Throttle Position(Manifold) = 25.49 %
EGR Commanded = 77.255 %
EGR Error = 0 %
Fuel Level (From Engine ECU) = 81.569 %
Barometric pressure (from vehicle) = 14.504 psi
Voltage (Control Module) = 14.45 V
Engine Load(Absolute) = 59.216 %
Commanded Equivalence Ratio(lambda) = 0.995
Relative Throttle Position = 18.824 %
Absolute Throttle Position B = 40 %
Accelerator PedalPosition D = 34.902 %
Accelerator PedalPosition E = 17.255 %


End of report.

For some reason st/lt fuel trim does not appear on the list?

Also, at a separate time entirely, i got another unique code which is the U0155; Lost communication with instrument panel cluster control module. I'm not sure if these are related in any way but it does lead me to think that my problems may be from a loose wire or something. Let me know what you guys think.

Re: Random cylinder misfire
 

What is the fault code number that triggered this batch of freeze frame data?

How many other codes were set, and were they set all at the same time?

Maybe it's there and you need to scroll up or down in your scanner to see it?

Wish I could plug my scanner in to see what it shows.


Not enough info. This code set at a different time than the problems above?

Which section of which control unit produced this code? Engine? Trans?
Did the D indicator start blinking when it set this code?
This code should not turn on the CEL but does cause the D to blink...and it should have set a batch of freeze frame data.....so what code goes with the data you posted above?

I think it's unrelated to misfire code issues.
I'd erase it and see if it resets the U code again later on.

Re: Random cylinder misfire
 

"How many other codes were set, and were they set all at the same time?"

The same ones as stated in the first post. Misfire p0301 p0302 p0303
p0304 p0300.

"Maybe it's there and you need to scroll up or down in your scanner to see it?"

i checked the freeze frame again for good measure and the fuel trim is there this time for whatever reason. It is within compliance

Freeze frame information:
------------------
Fuel Status = 0 byte
Engine Load = 78.431 %
Engine Coolant Temperature = 190.4 °F
Fuel Trim Bank 1 Short Term = -2.344 %
Fuel Trim Bank 1 Long Term = -2.344 %
Intake Manifold Pressure = 11.603 psi
Engine RPM = 2,601 rpm
Speed (OBD) = 79.536 mph
Timing Advance = 31 °
Intake Air Temperature = 89.6 °F
Mass Air Flow Rate = 25.94 g/s
Throttle Position(Manifold) = 25.49 %
Run time since engine start = 2,957 s
EGR Commanded = 77.255 %
EGR Error = 0 %
Fuel Level (From Engine ECU) = 81.569 %
Barometric pressure (from vehicle) = 14.504 psi
Voltage (Control Module) = 14.45 V
Engine Load(Absolute) = 59.216 %
Commanded Equivalence Ratio(lambda) = 0.995
Relative Throttle Position = 18.824 %
Absolute Throttle Position B = 40 %
Accelerator PedalPosition D = 34.902 %
Accelerator PedalPosition E = 17.255 %


End of report.

"Which section of which control unit produced this code? Engine? Trans?
Did the D indicator start blinking when it set this code?"

I didnt notice the D blink but it has done that once before but not while misfiring.

"This code should not turn on the CEL but does cause the D to blink...and it should have set a batch of freeze frame data.....so what code goes with the data you posted above?"

when you say batch I think i know what you mean. I can keep pressing next freeze frame on the scanner but all the values are similar so i didnt find it usefull to post a bunch of them

Re: Random cylinder misfire
 

Only a single fault code number goes with that freeze frame data, it cannot be for all of the 5 different P codes listed.

The PCM only stores the freeze frame data for a single code, though it can be overwritten by another code if it has a higher priority.


I was referring to your ff data you posted as "a batch", but I don't think it's actually called that by the engineers that thought it up.

Trims look fine, lambda looks normal, nothing really stands out as unusual in the data you posted. It gives me a good clue of how the car was being driven when the data was set, but it doesn't give any answers to the root cause (and it's not really intended to, much of the time). I'm not really sure what to tell you on this right now.....I'd probably need to experience it firsthand if possible


Wasn't driving on a rough road there when it set, was it?
If you hold the RPM at 2600 for while (without driving it) will it set misfire codes? After driving it around to get it all warmed up first?

I know these aren't known for ignition coil failures like some other engines are, but what about that possibility?

Re: Random cylinder misfire
 

I drive 180 miles in a day 3 days a week. i also do plenty of city driving. It will only happen when driving on the freeway after driving for a while. It doesn't happen every day i drive the freeway nor does it happen in the same place every time. The freeway where i drive is not bumpy. There is no noticeable jolt or feeling of misfire when it happens and no performance difference. Sometimes it goes into manufacturer control but other than that just a cel light.