Yuen001

Hey Everyone,

My car is a 2003 Civic Coupe EX automatic transmission with 260K miles on it.

it is coming up with DTC codes P0300, P0301, P0302, P0303, and P0304.

which means random multiple misfire, misfire cylinder 1, misfire cylinder 2, misfire cylinder 3, and misfire cylinder 4.

it really only misfires when the car is warm. and under light throttle. sometimes the CEL will also blink. which means that the misfires are bad enought to cause damage to the CAT and it kills fuel to the misfiring cylinder.

you can hear the engine ticking from the misfiring.

i've been trying to troubleshoot this for over a month now and it is pissing me off.

the car is bone stock. no mods at all.

here's what i have done already

- replace all spark plugs with NGK platinums
- replaced all coil packs. this car has the coil on plug stup. no distributor
- replaced the PCV valve, the old one seemed ok, but seapped it anyway.
- replaced the EGR valve. old one seemed ok but did it anyway.
- looked for vacuum leaks, did not see any. confiremd with a vacuum test. read 20in at idle.
- checked out all the fuel injectors, they looked good, used fuel injector cleaner anyway, twice. used Lucas Oil Fuel injector cleaner in the tank. the seals looked good too, still soft and rubbery
- replaced the air filter with a K&N high flow air filter. the kind that goes in the air box .. not a short ram.
- cleaned the throttle body with carb / throttle body cleaner.
- did a compression test, read 180, 190, 190, 180 on cylinders 4,3,2 and 1 respectively.
- if it had a fuel filter i would replace that too. but the fuel filter is in tank and it is the coarse sock type filter.
- replaced the ELD, no codes came up for this, but i heard there was a munufacturer defect on them so i replaced it anyway.

i have almost run out of things to check and replace on this thing.

the misfire codes don;t come on all at the same time. usually P0303 comes first and then the rest follow a shor time later. i've swapped injectors from cylinder 3 to 1 and the misfire still comes back as P0303, which would mean it's not the injector.

what do you guys think ?

anyone else having this problem ?

thanks


Modified by Yuen001 at 9:24 AM 10/29/2008

saviourkakashi

I would guess ECU is bad

Yuen001

i thught about that, or the ICM (if it is separate from the ECU). but if that were the case, it would misfire all the time as oppose to just when it is warm. plus the ECU is big $$$

RISRdotNet

try replace your knock sensor

RISRdotNet

does it eat coolant or oil? do a leakdown if possible

Yuen001

the fluids are good and the oil level is good as well. i thought about either the Crank sensor or the TDC sensor. but if either of those sensors were bad, i would get a DTC code, which i do not.

unless the signals are still in range but not correct. does anyone know how to test these sensors ? what signals i should be getting ?

the TDC sensor shouldn't be too bad to replace. but the crank sensor will be a PITA to get to..

thanks for the help guys

saviourkakashi

could be possible oyu have a short which is affecting the signal to your coilpacks. This may sound silly but check your alternator fuse.

Yuen001

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by saviourkakashi &raquo;</TD></TR><TR><TD CLASS="quote">could be possible oyu have a short which is affecting the signal to your coilpacks. This may sound silly but check your alternator fuse.</TD></TR></TABLE>

yea, i thought of the wires too, but if that were the case it would not matter if the car is warm or cold and i am only noticing the problem when the car is warm.

the problem has been going on for many months now, if it were the alternator fuse, i think i would have a dead battery by now. but i will check the alternator fuse as well as all the other fuses.


Modified by Yuen001 at 11:18 AM 10/30/2008

Yuen001

replaced the TDC sensor today .. didn't help .. still misfires. checked some more stuff over the weekend that didn't help. checked to see if the CAT was clogged. and changed the plugs again. still nothing

could the o2 sensors be bad ? i was comparing it to a buddy of mine's car which was a non v-tec civic. but his o2s1 read mostly high ~0.8v but bounced areound and his o2s2 read most low ~0.12v. where as my civic, the o2s1 reads mostly high but bounces around between 0.2v to 0.8 v .. but my o2s2 reads high as well. about 0.8v

does anyone know what the signals should be ?

thanks

saviourkakashi

When my O2 sensors were bad my car misfired big time. It's a very good possibility the sensors are bad. Give replacing them a shot.

Yuen001

approx how many miles did you have on the o2's and did you get a DTC for them ?

i think i'm gonna give replacing them a shot. debating whether i should change the CAT as well.

saviourkakashi

The sensors malfunctioning were bad b/c the wiring got burned on my race headrs. Regardless, the sensors were malfunctioning and it caused serious misfiring.

Yuen001

thanks for the input, i'll put some new ones in and look into changing the CAT and see what happens ( fingers crossed). i'll keep everyone posted.

thanks

saviourkakashi

If the cat were bad you would def be getting a code for that. Going with the O2 sensors first is a good move

RISRdotNet

did you replace your knock sensor, i can't find that you did anywhere in this post

cooter82

Yuen001,

Di dyou get it running right yet? I have same problem on my 2000 civic. I replaced the ICM yesterday because it indicate dbad on the tester at Advance Auto. i stood there and watche dthe guy and he did the test twice. Anyway it didn't fix it after the 100.00 I paid for it. I hate to start swapping parts out like you did so I'll probably shoot some wires and the coil and then call it a day. So dar i changed plugs, wires, fuel filter, ICM, distributo cap and rotor. Was running OK whencold and terrible when hot, not it runs like crap no matter what.

cooter82

Yuen001

i needed a vaca from this car, i did not replace the knock sensor .. i hear it is a pain to get to and usually would get a code if the sensor was bad.

i did replace the O2's before i left and that did not help. something seems funky with the CAT but it is not what is causing the misfire.

I checked again for Vacuum leaks and found nothing. i am seriously running out of idea's. i'll do some research on the knock sensor.

thanks

Yuen001

are you getting any codes ? the only codes i was getting was P0300, p0301, p0302, p0303, p0304. and that was it, which gave me no clue as to what the problem could be.

are you getting misfires at idle ? which cylinders are misfiring ? what is your timing set at ?

just to get a better idea as to what is causing your misfiring.

F40

It could be your cat. I just went through the same thing with my EK and it turned out to be my cat.

Yuen001

did you get any codes before you replaced the CAT ?

a test that i did was i bypassed the cat by simulating the correct voltages on the doenstream o2. i hooked a scope up to the up stream o2 and the waveforms were correct.

with the proper voltages, i took it for a drive and NADA.

postman

unclog your egr passages in the intake - fixed

Yuen001

if they were clogged, i would get an insufficient egr flow code. but i did it anyway when i replaced my egr valve.

unevolved

That sucks, dude. Troubleshooting is the worst.

I can't find anywhere that you've replaced or ruled out the O2 sensors, right? Seems like that's the only thing that could be wrong left.

Cars don't just "not work." There's always something wrong if they're acting up, it's just a matter of finding out what.

Yuen001

yea, i replaced the downstream o2 and tested the upstream one. didn't help the situation. i was so sure it would be the o2's too.

the only thing i haven't swapped out is the ecu. those are a pretty penny

postman

if im remembering correctly off the top of my head, between your intake manifold and cylinder head is your egr flow plate in the plate are tiny holes which get clogged. that is where the clog happens and slows down if not completely block flow. it will not trigger an insuff egr code. the only way to clean it is by removing the intake