Hi everyone!

I am getting occasional random misfires on all six cylinders. I've been getting this for the last two years or so now. The misfires seem to only happen when the engine is started cold and is allowed to idle cold. If I start cold and hold the throttle around 2500rpm and let it heat up, the misfires don't happen.

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It starting happening last year right around winter here in NY, and then come spring the misfire codes stopped happening, they stayed off all summer and fall.

They came back again this winter.

There is also a pending p1399 code that never fully reads as a code, just a pending code.

Within the last two years the car has had:
Valve adjustment.
EGR passage cleaned.
New EGR valve.
New plugs and coils.
New PCV valve.

The car is at 202k miles and is about 20k miles away from a timing belt.

I've checked the IAT sensor and it seems to be reading voltage as the car warms up, and the resistance seemed normal.

I also checked the IAC valve, and it seemed to be working too (idles around 650rpm after warmed up)

The purge control solenoid is very loud. I can hear two distinct sounds in the engine compartment, the engine running, and the purge control solenoid clicking. Could this be failing?

Does anyone have any suggestions on what to check next? I'm trying to sell the car, but don't want to sell it with the check engine light on.

Thanks in advance!


Update: I had it idling for a while this morning and it was fine, no lights. I held the rpm around 2500 until the coolant fan came on, so the engine was hot. Then as I pulled out of our parking lot (not even 20mph) the light came on for random misfires and pending P1399. I pulled out the IAT sensor and cleaned it good with some carb/throttle body cleaner (it was practically black with build up), no idea if that affected anything yet.. I'll start it cold tomorrow and see how it runs.

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If you have verified good spark and fuel at the cylinder, you could check test the compression and preform a leak down test.

Another thing to look at would be the engines fuel trims at idle, you may have a cold idle vacuum leak.

 

Try taking your catalytic convert off and driving it. Yeah, it's LOUD so you're going to **** off the neighbors if you have them. I am working through the same issues (after timing belt, valve adjustment, new plugs, new distributor, new fuel filter, most of which were needed anyway). It would idle all day in P or N without codes. I don't have a definitive answer because I just ordered a high flow cat so I have not installed it yet. But I had all 8 misfire codes and the only one that came back after driving without a cat was 1399 (and the missing O2 sensor of course). It is concerning that the 1399 came back, so I am not positive about my answer. I have a 98 CL with the J30.

Update: replacing the cat did NOT solve my problem.

 

Thanks for the suggestions all. Unfortunately, there is not a lot that I can do any more since we're renting in a condo complex this year, and they have policies on car maintenance in the parking lot (working on moving somewhere else with a garage hopefully), so a lot of this I've had to do 4 hours away at my in-laws or at my work parking lot.

Back about two years ago when this started, the car went from running great to stumbling and flashing the check engine light in less than 60 seconds. Took it to the Honda dealership where they said to do a valve adjustment and clean the EGR passages. We got it back, drove it away and the check engine light came back on immediately and started flashing, so we drove it back. They said the only other thing they could do, and didn't recommend due to cost, was to try resurfacing the valve seats. The tech who was helping us at the time said to try putting Seafoam in the oil instead, which miraculously did clean up the misfires and quiet the engine down.

It's just odd to me that they are coming back now in the winter. The last thing I can think to do easily here (and in the middle of winter) is to put a few gallons of premium in and see if that makes any difference. I read that these Hondas suffered from heat soak due to the winter blend gasoline they use, so maybe that would explain why things don't work right in the winter, but they do in the late spring/summer? Not sure... but, worth a shot. I have some injector cleaner mixed in the current tank, so I'm trying to run that out before I put anything else in.

Because we want to sell it, I don't really want to put a lot more into it, but I think I'll take to the dealership (different one than we went to 2 years ago) and have them listen to it and see what they think, or some local shop that sounds reputable (just moved to the area, so not very familiar with the shops yet). I'll have them do an oil change and I'll put more Seafoam in the oil too and see if that really is the magic fix for the remaining life of the car.


I will absolutely keep this thread updated as I learn more and if I hear anything from Honda or a local shop about it.

 

Check your air box where your air filter is located. This happened to me and it was because the car was getting too much air through the cracks in the air box. It was messing up my fuel air ratio.

 

Update: I got it back from the shop and they confirmed what Honda told me two years ago, it probably needs a valve job. They suspect there's something up with the valves causing it to idle rough and throw misfire codes.
I will be selling it and moving on, as I've already put to much time and money into chasing this problem. If I had a garage I'd already have the heads off and I'd be doing the valves myself, but oh well. It's got 200k miles on it and it's lived a long life.

Thanks again for the suggestions.

 

"Probable" cause? did they perform a leak down test?