3 confirmed cylinder misfires and one random misfire


Asked by Oct 10, 2014 at 09:12 PM about the 2001 Honda Civic Coupe EX

Question type: Maintenance & Repair

I am struggling with MIL coming on. I am getting 3 confirmed cylinder misfiires (P0301,P0303,P0304) and random misfire (P0300). Car seems to be running fine, perhaps , if any, with a little less power than before. View  Freeze data shows
Trouble code P0303
ABSLT TPS(%) 24.3
Engine Speed (RPM) 2494
Calc Load (%)  80
MAP ("Hg) 23.9
Coolant Temp (F)  190
IAT(F)  97
ST FTRM1 %   9.4
LT FTRM1 % 3.9
Vehicle speed (mph) 41
Fuel Sys1 CLSD
Fuel SYS2 n/a

Could someone familiar with this car and these issues please let me know what might be causing these reading and MIL coming on?
car is 2001 honda civic ex coupe at about 160K miles.

34 Answers


I forgot to mention, spark plugs and ignition coils were replaced early on this week because of occasional engine light coming up and with misfire codes measured lately. Changing plugs and ignition coils did not help to cure the problem.

9 of 9 people found this helpful.

Check the fuel pressure,may just be clogged fuel filter or fuel pump,not having good fuel pressure,will cause this.

6 of 6 people found this helpful.

Thank you. I will get it checked tomorrow and will post the result.

4 of 4 people found this helpful.

I took it to an autoshop. They suggested to do full diagnostic for $89.95 (plus tax) instead. I was assured it will show the source of the problem including fuel pressure problems. I agreed. Mechanic said he first found P0303 and the code became P0302 after he switched ignition coil on cyl 3 with the one on cyl 2 suggesting that coil on cylinder now is bad (he said he temporarily fixed it but I should get it replaced soon). He also said that his measurements show fuel injectors need cleaning and one can of fuel injector cleaner put into a fuel tank of gas should fix the problem. he said he does not see ay problem with exhaust (catalytic converter) I later put 1 can of fuel injector cleaner and 1 tank of gas and drove car for about 20 miles. MIL was still off. Even when assertion that coil no 2 is bad contradicted my experience (as I also switched coils at on point and failing cylinder stayed at 3) I thought he perhaps saw something wrong (marks) on the coil that is cyl. number 2 so I returned it and replaced with a new one. a few minutes later MIL came on and guess what: code was P0303. This tells me there is still something wrong on cyl 3. I am hoping one can of injector cleaner will clean the injector on cyl 3. I will post if I still have problem. By the way is there harm in using fuel injector cleaners frequently. For example if this can does not fix the problem can I add another can at the next filling of my gas tank?

5 of 5 people found this helpful.

Now I have P0301,P0302,P0303,P0304, P0300 and P0420 all confirmed and P0301,P0303,P0300, and P0420 pending. Car is running OK perhaps a little rough. What is going on? Any experienced person cares to comment?

8 of 8 people found this helpful.

I have the exact same thing with my 99 civic. Did u ever find out what it was? If so please let me know. I have changed my spark plugs, wires, cool, rotor, and cap. I put chevron fuel injector cleaner and I'm still getting all misfire on all cylinders and random misfire.

7 of 7 people found this helpful.

Hi Vee. No I did not find out. Same thing is still going on. I have other issues (accident) with the car to deal with. I will try to address that problem later.

1 of 1 people found this helpful.

I actually took it to a friends mechanic and it turned out that one fuel injector was not working properly. I replaced that one and it seems to be running fine for now, mechanic did say that he also thought that fuel injector on cylinder 1 might need to be replaced. I don't know if you have replaced them but I suggest that if you have not then doesn't hurt to try also advanced auto parts online has a $50 off $125 (WD47) promo code. or amazon is cheap FYI

2 of 2 people found this helpful.

I just had the same problem with my 97 civic p0303 and p0304 my initial thought was egr valve cause its right next to cylinders 3 and 4 so I pulled it off cleaned it out cleared the codes drove it was still missing but only on cylinder 3 this time so I uplugged the egr no more misfire or misfire codes

4 of 4 people found this helpful.

Thank you Josh. you might be right. I did not check EGR yet. Replacing PCV helped me, I thought at one point, but I still get p0303, p0304, p0300 after 100 miles or so driving. This is actually puzzling why I dont get them right away. On EGR valve I could replace it if it not too expensive. You mentioned unplugging the EGR valve, I suppose you meant for testing purposes. I would think you will get EGR related codes from the computer when you do that.

2 of 2 people found this helpful.

I am having some of the same problems. 2001 civic lx 186,xxx. Tried bleeding radiator and a day later engine light come on took to autozone said it was misfiring on 3 cylinders. I have no idea heard it could b plug wires

3 of 3 people found this helpful.

Hi 01civic. I don't think bleeding radiator would have anything to do with it . I am inclined to say that it is probably clogged EGR ports with my car, I still didd not dare to clean them. it is very involved. Check plugs and wires in your car but I would think, you might be suffering from clogged EGR ports if plugs and/or wires are OK.


I know this thread is dead but I have a 98 civic LX 5MT...I started having misfires making me lose power until eventually i was misfiring on ALL 4 CYLINDERS..paid $80 at a shop to have them unclog my fuel injectors. That was 2 years ago and I haven't had a problem since.

1 of 1 people found this helpful.

Just dropped my sons 2010 Honda civic hybrid, car was mis firing, and could barely drive but made it to mechanic, guy says all 4 are misfiring not sure why, thought we put not good gas or something. And all lites on dash board are lighting up. I sure hope it's nothing too bad.

6 of 6 people found this helpful.

I just bought a 2002 civic ex was have the same miss firing codes replaced 02 sensors, spark pugs, and cleaned egr valve and was still getting check engine codes ... removed the air regulator box and codes gone and still runs fine !!

2 of 2 people found this helpful.

I have the same problem on my 2003 civic ex, sedan. I replaced the spark plugs and coils. I cleaned egr.Drove for a month the engine light went on so I parked the car for a week. After a week I started the car no engine light. I bought a Obd2 scanner...it is showing p0301,p0302 and p0303. Help.

7 of 7 people found this helpful.

I've had same problem 2001 honda accord after replace a few thing and had valves lashed at 120,000 in which they say should be done around 60 to 80,000 come to find out my o2 sensor was bad replaced it car has been running perfect since, wires were melted together on o2 sensor

4 of 4 people found this helpful.

Thanks, i will replace both then let you know.

Hello everyone. So I got a few codes on my 96 civic dx. 4 of them are 1-4 cylinders misfire ( but I replaced them about less than 2k miles ago) P0420 and P0141. So I took of both o2 sensors and they looks rusty so I just replace them. Wasn't super tight but tight enough ,hope it won't matters. And the catalytic conversation looks normal: light brown with NO carbon build up at least , so it doesn't need to be replaced. The problem now is the engine light still on and sometimes flashes, and car lose power due to misfire problems. So what's next need to be checked and replace? Thank you

did anyone hear from necatig??? was it EGR??? have 02 civic lx same intermittent CEL, replace plugs, goes away comes back...coils...same...


Hi Tom_o. No I did not respond anymore. I never found the source of the problem. I sold the car. [ We had a severe body damage due to an accident that happened around that time ; I struggled with fixing those problems for a while. A later got to the engine light problem.I got the injectors cleaned. Did not help. Could not check the fuel filter as it is in the gas tank. Cleaned egr wave and some part of egr passage entrances that I could reach, Did not help. Cleaning egr passages completely was out of question for me as it involved tremendous amount of work (or cost if I chose to get it done in a shop). The car was not worth spending money on it anymore. As I said above I sold it (at a junk yard price). What a pity. ] The whole thing is was very puzzling though. The car was running near perfect during all these struggles. No hesitation, no noise, no dying nothing. Just the darn engine light. Something got out of specs for the ECU obviously.

wow...that's what my wife wants to do, trade-in, it's here car....and with the flashing CEL the car WOULD misfire and jerk. now the temp gauge is rising at stop, may be leak at head gasket lots $$$$ sigh.


Okay guys... this is your Honda Civic specialist.. P0 300, P0 301, P0 302, p1399.. all of those are misfires, what's happening is you have more spark than volume of gas,, just change the fuel pump.. on a Honda Civic the fuel pump will jump down to 38%.. you need 100%.. it's the fuel pump trust me...

3 of 3 people found this helpful.

Have similar probs on 96 integra.... new dizzy, new injectors, new pump, filter, lines, plugs, wires, crankshaft sensor, belts including timing, map, fuel pressure regulator, ecm...was misfire cyl 1, reset computer, now misfire 2 and 3... not actually misfiring.. what's happening?? ?Had to rig the return line (clamp it additionally with extra hose and clamp) to get it to run correctly. Runs perfect for a week or so then doesn't run again - have to tighten clamp.. .HELP!


Have a 2002 Civic as it drove fine as bought with engine light already on. Though when driving odd time the car bogged for few second but went away this time the bogging wouldn't stop and engine light came on flashing now. Anyone have this happen in their civic. Scanned and said obd2s also misfire cylinder 2 forgot the codes atm but any help?

1 of 1 people found this helpful.

Hello, Can someone advice please. I have honda civic 2003 1.7 VTEC. Light has been on for at least six months. Showing P0300, 301, 302, 303, 304. I changed spark plugs. Changed cylinder 1 ignition coil. After few miles light came on. Starting with p0301. Amy idea??


Change the fuel pump..... same thing happened to me a few months ago..... was not receiving correct volume of gas

1 of 1 people found this helpful.

I am inclined to agree with G0381 on Fuel pump being likely source of ongoing engine light problems. As I mentioned early on the thread that was the only thing I did not do fix the engine light problem on 2001 Honda Civic EX. and the problem remained.

Pappoosp 123 about a second ago Best Answer I went to a service centre to ask whether they can change the fuel pump. The recommended a local garage. The guy at the local garage was very helpful. I explained what I have done so far. He explained the I changed the coil in cylinder 4 not 1 as I thought. And there was no misfire showing from cylinder 4. He had a quick look raving the engine and suggested that he can't see any problem with fuel injector or fuel pump and said go ahead with my plan changing remaining ignition coils. I came home and tried swapping the coil and still got misfire from the one I put the new one. I will talk to the guy next week. But i am Not sure whether it is worth changing it as the car has no resale value due to its age but I already spent nearly £600 on break disc, pads,caliper, plugs and coils. I could have bought another cat for bit more money, now it's not worth getting another one after spending all the money. I am a bit confused


Recently I had my car engine misfiring on cylinders 1, 2, and 4. It could not keep the engine running smoothly. Result: I went to Advance Auto Parts in my city (in NH) and the insignificant diagnosis they made was right. The spark plugs needed to be replaced. Nothing else. Not even the coil was bad. I bought four NGK spark plugs, Part Number 7100, which cost only $ 11.70 with a 20% discount on the Advance website. NGK are great ignition plugs manufactured in Japan. Now my car is running smooth. I hope you have the same luck. Do not be fooled by dishonest mechanics who want to fix what your car does not need. Good luck.

2 of 2 people found this helpful.

I have a 2002 civic ex. My maintenance required light keeps flashing on startup and the start up is a little shaky. It gets better almost instantly after driving for a few minutes. I used a diagnostic tool and got the misfire codes P0302, P0303, P0304 and codes P0401 (EGR system insufficient flow detected) and P1457 (EVAP system leak detected canister area). What should I do? The guys at autozone said they don't have a clear solution and suggested I google the answer.

All the above answers are very typical routes to go... none are correct. It's the cam carrier bracket on the head and/or rocker arms. Take it to a better mechanic next time.

VERY seldomly you can get the same thing from a bad ignition coil (NOT coil pack) but that's more common in Fords

Have any if you experiencing misfiring issues tried replacing cam shaft sensor? I have a Pt Cruiser (I know different make) and was experiencing misfires (codes 300&3003). I replaced coil pack, spark plug wires, spark plugs, cleaned and tested each injector..... and the money kept going. But thankfully a friend suggested checking my cam shaft sensor. And let me tell you, she runs like a champ now.

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