8888

I actually have done some research on this problem but I can't get the behavior of the problem to match any specific cause, so I thought I'd throw this out there in case someone has seen it before.

My son bought a 2000 Accord, actually, I bought it for him, as a daily to run back and forth to work, school etc. One owner car with 160k owned by a GE aviation engineer, all records, everything had been done (clutch/timing belt were the big ones I was looking for). It had one problem.....a CEL for misfire that would show up after the car ran for a while. The car ran really well and the mechanic who had done all of the work on the service records confirmed it was not a mechanical/compression issue and it ran too well on the test drive for me to suspect that. No smoke, no uneven idle, nothing pointed to a serious issue.

So I buy the car and pick it up a few days later, he is still driving it back and forth to work till I take possession. On the way home from Cincinnati, the CEL comes on as usual but I get an increasingly rough idle when the car is stopped. The CEL flashes occasionally when stopped and idling. Car runs fine otherwise, mpg seems reasonable based on the gauge and miles traveled.

I get home and scan it and sure enough, I have P030x misfire codes for all cylinders except number 2 and a P0300 as well. I start just having a look around the engine compartment for loose/bad vacuum lines etc and find the PCV valve doesn't rattle. Some air passes through but it's not rattling. So I replace that (and the PCV hose to the manifold on general principles since it's pretty hard) and I am rewarded with an immediate CEL (versus having some time elapse before it appeared), I still have a rough idle, and I now have P1399 pending misfire on top of the previous misfire codes.

There is no sign of any play in the distributor shaft that would affect the rotor versus the cap. Looking back at the service records I see OEM cap, rotor, plugs, and wires were done in December of 2014, no sign of a coil replacement, so I decide to swap the coil with a new one.

Bingo, the car starts with no CEL and idles like a dream. I shut it off, and the next day I take it out for a drive around and it's fine. My son takes it out for a drive around the next evening and it's fine, He drives it to work and it's fine, at lunch that day the CEL comes back and when he brings it home, it has the rough idle with occasional CEL flash. I scan it and I get P0303 for misfire cylinder 3 and P1399 for pending misfire.

At this point, I figure that there must be something in cylinder 3, loose plug or plug wire but I decide to pull the plugs and see what they look like while checking cylinder 3 plug and wire. They put NGK Iridiums in there December of 2014 so they should be good but I've heard some high end plugs don't like a condition that might foul them (thinking of the PCV valve) so I get some NGK V power coppers.

Maybe I'm wrong but I find nothing wrong with the Iridium plugs I took out, they all look fairly normal. Two are a little darker as you can see but when I've seen a bad cylinder, it's pretty obvious on the plug...black/wet, black/dry, gas/wet etc.



I fired up the car with the new copper plugs after gapping them to .044" spec and I get an immediate CEL on starting the car and now I have P0300 through 305 and the P1399 for pending misfire. I didn't let the car run longer enough to totally warm up and see if I would get the flashing CEL for a rough idle or not but I assume so. I'm thinking about putting the Iridiums back in and see if I go back to just cylinder 3.

I have seen some cases on the web where the valves on the 2.3 get tight and can burn and create misfires but if that was the case, why would the new coil fix it for a few days? That's not going to solve burned valves. Why on different cylinders at different times? Shouldn't I see some evidence of that on the plugs?

I'm kinda stumped.

Could this be something in the fuel injection system versus the ignition system? I think everything in the ignition system has been replaced, I'm assuming the Denso cap rotor and wires are still good.

Maybe the in tank fuel filter is clogging? I don't call seeing that in the records but may have missed it.

This car has a deep well for the plugs so my compression tester won't reach down there, as noted, it just doesn't seem like compression to me but I could be wrong. I could have a valve adjustment and compression test done on general principles, I guess?

We sold his Legacy GT so this will now be his daily back and forth to Dayton and to Lima on weekends and I would like to get it sorted soon. Any suggestions would be appreciated.

Thanks

origamy

Yes, it is a good idea to check if valve clearances are up to spec. Then compression test. If these are normal, I'd check for EGR problems. ICM can be failing too.

holmesnmanny

clean out the egr ports and the egr valve

8888

Thanks for the replies. I saw the EGR cleanout in the FAQ but I'm not getting the P0401 code. It doesn't always show up?

I saw links for other years, nothing for the 2000 unless this one is what I'm looking for?

https://honda-tech.com/forums/honda-...-code-2674082/

Thanks again.

MAD_MIKE

It's a speed density system, it's not the best or quickest at self diagnostics.
EGR port partially blocked would reduce EGR to all cylinders and would cause misfire issues at part throttle(cruise) speeds.
If the valves are too tight(they should be checked/adjusted every 30Kmiles) they will cause a misfire through out the range, including idle when hot.
There may have been other issues or you cleaned bad connections when the coil was replaced initially, but the same problem persists so it is not the coil.

Just because someone says they did something(including a paid mechanic) does not always mean they did, or did it correctly.
Check the valve clearance with the engine cold, albeit you will find the exhaust valves are too tight.

8888

Thanks for the replies.

I've been out of town and made an appointment with a shop uptown to set valve clearance today and if the CEL reappears, to do a compression test. Waiting to hear from them.

Last night, I drove it to the shop, that was the first time I had driven it since installing the V power plugs and it actually had better response than it had with the Iridiums and the idle, while rough, was not rough enough to cause the CEL to flash. The CEL comes on immediately and stays on, though. I didn't bother to scan it.

Even worst case situation with the old coil and the Iridiums, the car drives smooths out and runs decently at all throttle positions once off idle. I haven't driven one of these before so it feels like it's a little sluggish and surge-ish on medium acceleration to me, but I have nothing to compare it to.

I'll use the results of the compression test to tell me whether I need to dig into the EGR or not. I've never seen any code other than the P030x or P1399 misfires, not the P0401 EGR, but if the valves are set correctly, compression is good, ignition parts are all new, it has to be something else and the EGR seems to be a good possibility.

MAD_MIKE

Surging at cruise speeds could be indicative of the misfire problem, it would be sluggish as the engine is not producing full power. I don't think the EGR code really comes on until the EGR is mostly or completely blocked. A restriction in flow would cause a misfire problem, PCM would adjust for the misfire to protect the catalyst. Until there was a major flow reduction or stoppage the insufficient EGR flow code may not be tripped.

8888

That's what I thought as well about the surge/sluggishness, the misfire is still there, the rpms are just high enough that I don't feel them individually like I do at idle.

I just called the shop and they did the valve adjustment, that took care of the misfires. They checked compression as a secondary test and it was in spec and even across the board. I think we need some seat time on it but the news is good so far.

I think the EGR might be something to look at soon, it seems to be a common problem.

Thanks for the input.

8888

So I'm not out of the woods just yet. My son picked the car up and drove it around last night without any problems. He was pulling out of the driveway after driving it for a bit and he stopped to talk while I was on the tractor. I asked him how it was doing and he said fine, and then said that the CEL just came on and started flashing again. I could hear it idling rough but he was headed out and I had to finish the yard before the rain got there so I did not scan it. He is at work today and I will hopefully see the car tonight and be able to scan it. I assume it will be the misfire again but we will see. It's my son's daily for work and school and out of town to see the GF so this is kind of a pain in the ***, I probably shouldn't have sold his Legacy GT so quickly.

At least I know the valves are set right and the compression is good. I guess it's time to look at the EGR system and hope that fixes the problem. I'll probably replace the injector O rings while I'm in there.

8888

Scanned it last night and it's P0303 so only on cylinder 3. That's good news, I'm down to only one place to look at the moment.

poorman212

Just for giggles, have you looked at the cap and rotor? Yes, the "records" show they were replaced ~two years ago but it is still worth a look....if nothing else they are wear items and don't cost that much

Also note, a flashing CEL/MIL is a bad thing

holmesnmanny

Ignition issues don't only happen when the car warms up, they happen at all times. Same with fuel issues. The egr system only works after the car has completely warmed up. The p0401 only occurs when the system sees no flow. Since you are throwing misfire codes for everything but the 3rd cylinder it's likely the issue is the egr system but if you want to keep mickey mousing around with this without messing with the egr system that's your choice.

Otadeo

Did you find a solution to your problem? I have almost identical simptoms.

user456101

I had, or rather my daughter has, a 2000 accord 4 cylinder with a misfire problem and it turned out to be the injectors. I tried spark plugs, wires, cap and rotor and coil first. Looking at YouTube, I found a guy who showed how one cylinder misfiring can cause multiple misfire codes by the way. Since new injectors are really expensive, I decided to swap them out with injectors from a good looking engine at a junkyard for $8 each, instead of many times that much for rebuilt or new. I just did one at first but ended up doing them all and they fixed the problem. I didn't originally intend to leave them in, it was just a way to troubleshoot the problem, made that much cheaper by the fact that the junkyard gives a 30 day warranty, and I could have just brought them back if they didn't work. Junkyards have a ton of these cars - the one I go to has at least 40 of these cars at any point in time.

Injectors are my guess, but the 6 cylinder accords of this vintage (all accords made from 1998-2002 model years are considered 6th generation accords and all have essentially identical innards given the obvious dichotomy between the 6 and 4 cylinder engines), they are really legendary for clogging up EGR passages (not only the port, but the passages from the port into the intake). Look for YouTube videos on this and you'll see. Ericthecarguy does a good one on a 6 cylinder honda accord "cleaning egr passages".

A channel called "Schrodinger's box" has the most thorough diagnostic troubleshooting videos on YouTube, but he has some diagnostic equipment you may not have on hand.

Otadeo

Thanks for the input. I'm particularly curious to see how user 8888 addressed the p1399 and p03xx. I read the p1399 can be addressed by a valve adjustment or cleaning the EGR and passages.

jollyhonda

A quick and easy test would be to swap the #3 injector with another cylinder and see if the misfire moves. Atleast now things are narrowed down to only a single cylinder causing problems, not the whole thing.

8888

It turned out to be an intake manifold leak. I took it to a shop and they found and fixed it via a smoke test and replacing the gaskets..