2001 Honda Civic EX MIL on with Misfire codes

dicator light (MIL) on for some time.

r being good perhaps. Anyways, recently I replaced the cap with the new one that I bought from the dealer and problem continued. Car was running OK.

and if I remember correctly also P0420.

es as their diagnostic tool was in repair at the time.

l pressure issues and that I should get it checked. I did that. Shop forem an used a fancy hand held diagnostic device with which he was getting misfi re in cylinder 3 and also random misfires. He suggested I add one can of f uel injector cleaner to a full tank of gas and that should fix the problem . He said he did not see any other problems.

oring codes myself. After resetting codes I would get P0303 (cylinder 3 mi sfire) after 20 miles or so driving.

inders , random misfire code (P0300) and P0420 which is related to catalyt ic converter in general. Freeze data only recorded P0303 related info.

P0420 is "catalyst efficiency below threshold" which means basically either your cat is shot or the downstream (of cat) O2 sensor has failed.

The misfires, you're just going to have to troubleshoot those... I would s tart with the misfire codes first and work on the 420 later, because a) fix ing that code is going to be expensive, unless you find a wiring fault rela ted to the downstream O2 sensor and b) a 420 code is an emissions failure, but that by itself does not indicate a problem that could damage anything i n your vehicle if you continue driving with that code present, nor does any thing that could cause it cause any kind of driveability issues.

before you dump a lot of $$$ in this car, have you started with the basics? Compression OK?

Another thought - if you're feeling down on power, can you drop the cat for testing and if you run with open exhaust does it feel like the power is ba ck? I'm not sure if a plugged cat will throw misfire codes but it will def initely cause you do be down on power and I'm thinking could possibly cause misfires... not sure why on #3 first and then the others though, I would t hink it would be all pretty random.

nate

Adsiz wrote in news: snipped-for-privacy@googlegroups.com: .

Check the ignition components and wiring.

There is a TSB (05-027) out for the '96-'00 Civic which blames poor igniter connections inside the distributor for very similar symptons. It's possible the same problem has developed over time on your '01 car, or there may be chafed wires somewhere.

dicator light (MIL) on for some time.

r being good perhaps. Anyways, recently I replaced the cap with the new one that I bought from the dealer and problem continued. Car was running OK.

and if I remember correctly also P0420.

es as their diagnostic tool was in repair at the time.

l pressure issues and that I should get it checked. I did that. Shop forem an used a fancy hand held diagnostic device with which he was getting misfi re in cylinder 3 and also random misfires. He suggested I add one can of f uel injector cleaner to a full tank of gas and that should fix the problem . He said he did not see any other problems.

oring codes myself. After resetting codes I would get P0303 (cylinder 3 mi sfire) after 20 miles or so driving.

inders , random misfire code (P0300) and P0420 which is related to catalyt ic converter in general. Freeze data only recorded P0303 related info.

Thank you Nathan and thank you Tegger for your valuable comments. I will fo llow up and perhaps post again.

wasn't there a bulletin for that?

Maybe not for 2001. But I think there's a bulletin for that for the 03 generation cars. It's an issue with the computer programming, that they fix with a flash.

Thank you all for replying. Interesting developments took place since my last post. Basically the probl em is still there but the pressure to solve it is less as I gave up and bou ght a small new car. I will keep this car in the garage and work on it or g et it worked on as I think of likely solutions.

Currently I am getting misfires on cylinders 2,3 and 4 and random misfire. If I drive some more I expect to get cylinder 1 misfire code as well. I had suspected this was due to mismatching spark plugs that a shop installed bu t replacing them yesterday with OEM plugs (NGK PZFRF-11) did not change the situation as I am getting misfires on the same cylinders. I now know plugs are good, ignitions coils are new and good, compression on cylinders are a ll good (around 170-180 psi) and there is no vacuum leak (smoke test is don e). Car is running excellent even when codes are on (not problem even with steady 70-80 mph speed). Having difficulty having all monitors (8 out of 8) getting ready. But occasionally I get P0420 when all monitors are set to r eady after days of driving, pointing to cat. But one shop (and Honda dealer ) said car could not run this good if CAT Converter was bad. Dealer suggest ed to get valve clearance check. I have some vibration front right, it is l ikely a warped brake rotor. I read somewhere that brakes and jerky transmis sion could be source of misfire codes. Do you think my vibrating brake (shi mmy?) could be causing the source of misfire codes?

By the way, Happy New Year everyone.

On my 03, there's a software flash to address this anomalous code.

My dealership service manager didn't hesitate to perform this. What the hell, it's money for him and takes only a few minutes.

Regardless, there was a service bulletin on this for 03. Might be worth looking into for 01.

Thank you Elmo. I will try to find out if there is a service bulletin for flash update for ECU for 2001 Civic EX as well.

That's BS. If the cat were PLUGGED, the car would run like shit, or not at all. But if the cat is just old and has gently worn out over time, which is what a P0420 suggests, then the car would run fine.

incorrect Valve adjustment is a legitimate possible source of misfires on Honda.

I doubt it, but the better question is, "is the car actually misfiring, or are you chasing phantom codes?"

GW

Thank you Geoff. I think you are suggesting ECU is the problem. If so, I wo nder if the flash update that was suggested earlier will be sufficient or n ot. I suppose I may need to get the ECU replaced. Does anyone know if ther e is a health check (self check) for the ECU?

Some updates;

• I have checked with the dealer: There is no flash update for 2001 Civic.

• I got fuel injector cleaning done at a shop. No change in misfire situat ion.

• No fuel pressure test is done yet. There is not fuel filter that can be c hanged in this model, only the sock in gas tank.

• I was told it is not possible to see if cat is bad by just inspecting it.

• Seems like there is a debate if a cat getting old could cause misfire cod es.

PS. Useful info: one who spends over $600 for fixing an emission related pr oblem but cannot fix it, and the car fails the state inspection test (due t o emission) in Texas twice within 60 days, and the car is OK otherwise, can get a emission inspection waiver for one year.

• I have checked with the dealer: There is no flash update for 2001 Civic.

• I got fuel injector cleaning done at a shop. No change in misfire situation.

• No fuel pressure test is done yet. There is not fuel filter that can be changed in this model, only the sock in gas tank.

• I was told it is not possible to see if cat is bad by just inspecting it.

• Seems like there is a debate if a cat getting old could cause misfire codes.

PS. Useful info: one who spends over $600 for fixing an emission related problem but cannot fix it, and the car fails the state inspection test (due to emission) in Texas twice within 60 days, and the car is OK otherwise, can get a emission inspection waiver for one year.

Same exempyion is available if the needed part is not available but the $600 expenditure requirement typically does not apply. I rode for two year on that exemption.

An aside the guy with the state found a used part (and remembered me) that allowed me to pass the next inspection.

Update:

I noticed I was having difficulty in getting ALL monitors ready. Also, cylinder 3 and 4 were giving misfire codes much earlier than cylinders 1 and 2 (but they eventually come on).

So, Moved ignition coils 3,4 to the position of 1,2 Changed PCV valve (seemed very dirty and stuck) Rotated Tires (which reduced clutch shuttering while starting at first gear) To my pleasant surprise misfires codes did not come on for quite some time. Instead I got all monitors ready almost immediately, however I got code P0420 soon after (which was taking long time like 200-300 miles drive, previously).

After a while P0303, P0304, and, P0300 (random misfire) came on. much later I got P0301 and P0302 as well.

As I reported earlier the car is running almost perfect. I wonder if it is now time to spend $130 at the dealership to get it diagnosed.

Any comments?