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I've got an odd problem, I think.

I have a 2001 Civic EX 5 speed with 223k miles on it. This is the first time I've experienced a serious mechanical failure and I bought the car with 60k on it. I have taken very good care of this car. I've changed the oil every 10k with Mobil 1 full synthetic and it only gets Chevron gas. All services are done (reasonably) on time.

It started about 3 weeks ago. I had just changed the timing belt (for the second time) on it and it ran great for a couple of days. Then I came home one night and it started to run rough. It felt like it was missing on one cylinder. The check engine light was flashing and the only codes I've read from it since this started are cylinder misfire codes on all 4 cylinders. The next day the car ran fine again. It began as an intermittent problem that gradually got worse. It seemed to be especially bad after the car was driven and then sat for a short time. Often it would run great the first trip of the day and then run bad the rest of the day.

Since then it's gotten much worse. It now runs like this all the time except for the first 5 minutes of the day. The check engine light constantly flashes. It's down considerably on power. I have to baby the clutch when starting out so it doesn't bog or stall. It definitely feels like it's missing on one cylinder.

Sometimes it will switch between running perfectly and running like crap. All of the sudden the "running like crap" will just kick in. It's like someone flipping a switch. The idle is rough and it shakes the whole car. If I rev it up to 2k it smooths out but I can still hear it running on 3 cylinders.

Again, the only codes are 300, 301, 302, 303, and 304.

I replaced the air filter, and the fuel pump, strainer, and fuel filter assembly. It runs exactly the same and I am not throwing another dime in parts at this problem until I figure out how to diagnose it. I am a pretty decent shadetree mechanic and I would much rather fix this myself but I'll admit this has got me stumped.

I'm about to go out and pull the plugs to see what they look like. I did not change them all that long ago. Maybe a year ago, or 15k at the most.

Any ideas would sure be appreciated!

 
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I pulled the plugs and they looked fine to me. Nice light tan on the tips and the gap is within spec.

Any ideas?

 
Rep Power: 519

Misfire codes for all 4, buy you say it's running on 3 cylinders, you should be able to isolate which cylinder is dead--if you are correct.



Got EGR? See if it's getting stuck open at idle. That would sure make it idle rough but get smoother at 2k....and snap out of it sometimes when the valve closes.

 
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If I'm getting misfire codes on all four cylinders, why do you think the problem is isolated to one cylinder? Wouldn't it be more likely to be caused by something that isn't specific to one cylinder?

That's a good thought about the EGR. The car is all stock so it's still there. Is there a good way to troubleshoot that system?

 
Rep Power: 519

I said what I said because you stated:

"It definitely feels like it's missing on one cylinder."

Codes be damned, if it's missing on a single cylinder that should make it a lot easier to figure out.
Some of their engines can set misfire codes on all cylinders even when only one is actually misfiring. The V6 engines will do this sometimes, one goes dead but the driver keeps driving, eventually all cylinders show a code..

If I feel a single cylinder miss but see multiple or all cylinders coded, I might clear the codes and then see which code returns first. (Only works if it's acting up at the time of testing.)


That's why I mentioned the EGR.
I'd use a scanner to watch EGR position sensor, compare when the car is acting right vs. when the car is acting wrong.


Maybe get the valve closed and car acting right, and disconnect the valve so it can no longer operate. Drive the car, see if problem is gone.



HTH