Stock: 2000 Honda Civic EX. 245k miles.

Sorry for the long post. - The short version is: My car is acting like its firing on 3 cylinders (intermittently) and running rich.

A week ago, I was driving down the interstate at 80+ mph. Everything seemed fine until about 30 miles into the trip. At that point i started to go up some hills. I pressed on the gas enough to make it maintain speed, or at least keep it from dropping more than 3 mph. Instead of maintaining speed, my car seems to loose some power and i drop almost 10 mph, my CEL light is blinking. I press a little more on the gas, and now the engine is vibrating a little bit, and it feels like the engine is misfiring. At the top of the hill, the CEL stops blinking. I can gently accelerate, but If i try any harder, the engine feels again like its missing and the CEL starts blinking again. This goes on over every hill on the interstate for the rest of the trip (CEL light, bogging engine). I try to take it easy on the car and do not go above 65 mph.

After i am off the interstate and waiting at the first intersection/red light, the car is idling a little rough. After driving on the highway for a while, the car will only intermittently act up.

I get home and check the spark plugs. I see normal (normal to me) gray carbon on each, but on one, there is a shade of black on one side, but doesn't appear to be fouled out.
At this point i will mention that my car has started to build up black carbon on the rear bumper for the past month or so (just a light coating).

After the engine cools, i head out again, and keep the speed below 75mph. This time i do not get any trouble.

The next day I am on my way to work, and some one pulls out in front of me, i have to swerve and floor the car for about 2 seconds to keep from hitting him and another vehicle. I immediately pull into a parking lot. My car is now idling pretty rough and acting again like its only firing on 3 cylinders. This clears up slowly.

I have now changed the spark plugs, dist. cap, and rotor (which were all less than 2 years old).
I have run a compression check, and i am getting: #1=170psi #2=160psi #3=170 psi #4=180psi (#1 being closest to the cam gear). [note: #2 is the one with the "black sided" spark plug].
I do have CEL code for P1457 (Evap leak) but i've had that since owning the car.
The CAT is just over 2 years old.
The O2 sensors are also about 2 years old (both DENSO).
The Coil is just over 2 years old.
I was running a Short Ram intake when all this occurred, but put the stock intake back on when i changed the plugs.
Fuel Filter is less than 6 months old (DENSO).
I will be running some fuel system cleaner soon.
I have been getting about 33mpg (mixed city/hwy) since it has started to get cold (i normally get 35-36 in the summer.

After changing the plugs, cap and rotor, i let the engine warm up. Once it was warm, i did hear the engine miss ONCE. I was not able to replicate it by revving to 4k RPMs and letting it go. I drove it for a whole day (gently) and have not noticed it miss yet, or the performance really change since before this started. But I am convinced this is not resolved.

I am a little paranoid that the CAT is possibly clogged, or on its way there, so that is coming out next week. I have also considered the ICM, or a faulty injector. Any other ideas of what I could check?


Since i am not sure if the recent issue is the same, or even related to one below, i'm leaving this till last:

This is not the first time i have had this issue.... I've had this car for about 3 years now. A few months after owning the car, i encountered something similar to what i am describing below. One night while driving in the rain, i hit a fair sized puddle. Shortly after, my car has almost no power, the CEL light is blinking, car is vibrating pretty bad if i step on the gas at all. I get the car home and let it sit overnight. Next morning... no problems at all. A few months go by, and its time for a tune up. I have the CAT replaced (its throwing a CAT related code at the time), replaced the O2 sensors, spark plug wires, dist cap, rotor, and the plugs. I still haven't noticed the problem since it first occurred. 6 months go by, and while driving home in 10 degrees, my car is firing on only three cylinders (shaking, no power, blinking CEL). The next day I replace the COIL. nogo. Check the plugs and wires, and find out that one of the cheap *** plug wires had been shorting through the boot into the valve cover. Once replaced, the car works fine, untill recently....

 

Yo man,

I have a 94 LS that is doing pretty much the same ****, throwing a Code 43 (fuel supply system) and I have yet to find the culpret. Some guys I work with suggested a clogged fuel filter or a plugged CAT, I will definitely keep in touch once I find out what is wrong with my baby.

 

also check your fuel filter and see if there are any air bubbles in there.
ive heard that this(what you explained) can happen.

 

About a week ago i did take off the CAT and replace it with a test pipe, and put on a new pipe and muffler. That made no difference. The old CAT appeared fine.

The car is still acting the same after driving on the interstate for a while, and after i have been climbing a steep, long hill.

I am starting to consider distributor failure, since a couple of people has stated that the igniter/ICM is known to act up only when hot. Unfortunately, one of the two screws holding the ICM in place stripped, so I will basically have to replace the whole dizzy at this point.


Edit: It just now clicked about you said with the fuel filter, but i would have figured that the system should prime all that out.

 

I'm having the same problems with my 94. it only does it when it feels like it. and especialy if i step on it, it seems like its missing randomly.

 

Sounds to me like it could still be a spark issue, since it has the most trouble under load. Is the coil hot to the touch?

 

I haven't tried taking the cap off after running the engine for a while, but i would assume all would be hot to the touch (not sure about too hot to touch, though).

 

The issue is still getting slightly worse.

Recap:
Only occurs when at normal operating temp. (Now) frequently occurs when idle. Occurs when driving, only when the car is under any strain (needs to down shift while trying to pull itself up a hill). Has not yet occurred while accelerating.

I have replaced: Dist Cap, Rotor, Plugs and Coil.

Wires appear in good shape (NGK wires - only 2 years old).

The ECU has finally detected a problem and now has the following codes:
P0302, P0304, (Misfire detected for Cylinder 2 and 4) and P0300 (Random Misfire detected).

Since its only happening while warm / hot, i can't see how it could be Fuel Pump or Fuel filter related. Since its also happening on more than one cylinder, I dont see how this could be injector or valve related (though i have run some fuel system cleaner twice).

I'm thinking maybe O2 sensor or ICM.

 

Well, just to start with, if you get a blinking CEL it means you have a dead misfire. That means it's detecting that one or more of the cylinders is completely misfiring. Since it's under load, I myself would think it's a spark issue. My 90 Probe GT had the same problem. It would be alright until you tried to get on it, then it would misfire. It turned out to be the spark plug wires arcing through the boots. I'd imagine it is a spark issue also since it's only after the car heats up. If it was a fuel issue you'd probably be seeing it from start up. Your compression numbers look good also (or as good as they're going to be for 245k miles). How recently were all those parts replaced? All 2 years ago or recently? Do you have and oil leaking from the spark plug tube seals onto the wires? Are you sure all the wires are sparking?

 

Dist Cap, Rotor, Plugs and Coil have all been replaced since the problem started. I intended to replace the Igniter/Ignition Control Module, but the screws stripped while trying to remove it. Once i save up enough, i may go ahead with a whole dist. replacement.

No oil leaking from the tubes, and no real signs of oil burning on the spark plugs themselves. Rechecking the plugs shows no signs of them fouling out.

I had an issue with one of the wires arcing through the boot before with this car, but that was only one wire, and the wires have been replaced with a better quality wire (2 years ago).

 

What wires are you running? A lot of the time the no-brand ones fail much sooner than a quality wire. I myself will only run NGK wires and plugs in my Hondas along with an OEM crap and rotor. If all those parts are good I'm assuming you have a problem with the igniter/ICM.

 

I am currently running a set of NGK racing class wires. To be sure, i am going to swap out the wires with another civic when i get a chance, Then Fuel Filter, then ICM / Dizzy replacement and post back with the results. Thanks

 

Today i replaced the fuel filter. no change.

I swapped out the spark plug wires for a known good set, and the problem went away.

In my mind, I never would have guessed all these symptoms would have amounted to the wires being the problem, for two reasons... They were a premium set of wires and less than two years old, and if I kept the RPMs high enough, the issue was not present.

Thanks for your input guys.