Rep Power: 0

I have a 02 Civic EX with 98000 miles on it and am getting the CEL once in a while. The only drivability problem is when crusising at about 40mph sometimes, the car stumbles/bucks when NOT accerlerating-a constant 40 mph. Sometimes the cel will come on for while and go away, somtimes for a day ot two. I have cleared the codes as well, the cel came back on both times i tried that after a few days. Have had the codes scanned twice and both times it showed p0300, p0301, p0302, p0303 and p0304. These show to be misfires. I have replaced the plugs and they are in good shape. Does anyone know the most common cause of these codes in our cars?

 
Rep Power: 811

usually misfire are caused by plugs or clogged injectors. did you use ngk v-power plugs or denso? any other plug brand will give you problems. are you losing any coolant (burning, not leaking)? if so it could be a small headgasket leak. could also be the coil packs on top of the plug. check the resistance of each one with a multimeter and see if they are all close to the same ohm value. if one is different, its bad.

 
Rep Power: 0

Gearbox -

Thanks for the answer. Not losing any coolant or anything, no smoking etc. Could you tell me exactly how to test the coil packs-I have a digital multimeter and know how to use it, but not sure where to test or what to look for. I have voltage at the plug fine, and i don't have any open circuits through the coils themselves-they all test the same. Fuel problem?

 
Rep Power: 811

it could be a fuel delivery problem, either clogged injectors or low fuel pressure (bad fuel pump). you can check the pressure but im not sure how its done.

 
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im having a similar issue with my 04 LX with 150000.. it misfires or 'bucks' only while hard acceleration... never while cruising, but all gears in hard acceleration in high RPMs about 5k and higher

 
Rep Power: 811

sounds like a broken engine mount?

 
Rep Power: 0

Check the fuel filter.. If not then i think the coils are bad... U can go to any auto store and ask em how to check if the coil is bad or not...

 
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hi, hoping for some help... these are some frustrating codes to break...
same codes,p0300 - p0304... heres the freeze frame on p0303, the first code that comes up... there are also a second set of these (p0300-p0304) codes which are all "pending"

fuel sys 1 cl
fuel sys 2 cl-fault
calc load(%) 91.37
ECT 190 F
stft b1 (%) 6.25
ltft b1 (%) .78
MAP 27.46
rpm 3277
speed 27mph
IAT 82 F
tps(%) 36.0

Anything listed there look out of wack???

i added lucas octane booster today, half a bottle and half a tank... the tank before this one i used lucas cylinder lube with injector cleaner on a full tank. (the freeze fram data above where from a 3 days ago, not after running the fuel treatment)

running ngk g-power spark plugs, before those i had bosch platinums, checked my coils (all with the same readings) and then rechecked, checked egr valve (not alot of carbon, less then i expected, clearly no blockage), i park in a garage and when i get out i can smell a funky odor from the rear, put my nose right up to the exhaust (car is off of course) and im almost positive it isn't coming from there... could be tho, i'm just getting over a cold and cant smell the greatest.. i notice there is a code for pretty much everything except the fuel filter, which i see in the manual needs a special wrench or socket, any ideas to that?? i have a garage full of sockets one should work right???..

The engine light will flash only when the rpms are 2700 or less, driving on the highway it never flashes (3000rpm at 100-110), when it does flash usually in 4th or 5th gear, stomping on the gas and watching the light it will flash quick and stop flashing, im assuming these flashes are the "only" time the car misfires, right??? or wrong???... but in the freeze frame it shows it happened at 3277 not far from 2700 but never have i noticed while cruising has it misfired over 2700 rpm


PAST PROBLEMS: (not sure if these would lead to anything causeing a misfire)
I had code for heat curcuit malfunction, due to a broken wire on the harness the o2 sensor plugs into(fixed this and no more code, was a p0141),

2-3 months ago i had the p0420, cat below threshold... since then iv replaced the o2 sensor on the cat (code went away, could this be because i erased it?? i know if its clogged it can cause misfires but like i said, no code stating otherwise)

Had the crank sensor replaced because of the code (code gone now, p0336)

 
Rep Power: 227

Start by replacing the fuel filter as you mentioned. Using two open-ended wrenches in a scissor-like action works best to loosen or tighten the nuts.

 
Rep Power: 811

in a 2002 civic the filter is a strainer inside the fuel tank, where the pump is. may want to check fuel pressure first before opening everything up. usually misfires are caused by low fuel pressure (clogged injectors or bad fuel pump), bad plugs, or blown headgasket. im leaning towards the injectors because its intermittant and the car drives fine most of the time.

 
Rep Power: 227

Thanks for the correction. I always forget that 7th gen Civics have the fuel filter in the tank.

 
Rep Power: 811

7thgen is the oddball of the civic family lol. they did so many weird things

 
Rep Power: 0

Whats up guys!!!! ok!!
-Fuel pressure test(very easy to make), it was 40"psi", 40-47 psi in my manual being normal......
-Vacuum test(just as easy, tighter spaces tho), it was 20 "in Hg", 17-22 in my manual, being normal.(started the car, went right to 20, holding rpms at 2000, it quickly went to 0, came back up to 25, then back to 20)
If i can get my hands on a 200psi gauge ill have some compression test data to add to this!!!!!!
by the way, both tests, both gauges, where steady, no jumps in the needle. there was a little jumping on the fuel pressure but im 99.9999% it was cuz of the engine running.

engine is not rough on idle, when the fan kicks in, my rpm's drop almost to 500 and it sounds like the engine is gonna stall but has never...
cleared my codes yesterday, and today p0300-p0304.... p0303, p0300, p0301, p0302, p0304 in the same sequence they come up on the scanner
only difference in freeze frame----
rpm's 2650 at 55mph
stft 0.00
ltft 0.00

 
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I had a similar problem with my 01 civic, same codes, turned out to be dirty injectors. I also cleaned the throttle body and intake manifold, had no lights or problems since. Good luck.

 
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project_em2 I know this is a very old thread but did you ever find out what was causing the misfire under acceleration?

 
Rep Power: 125

Have you tried any of the suggestions in the thread? i.e the one right above your post?

 
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Chezboat24, I have tried almost everything I’ve found on this site and others. I recently installed this engine myself (low mileage used JDM) and believe me this engine is clean as can be. Also I’ve heard that if you can power out of the misfire instead of stalling, it’s ignition related. Can anyone confirm? I also have created my own thread explaining my situation in extreme detail.

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