A little help from the Hive? Cousin is chasing a random misfire on his Accord, 1999 V6 auto w/192k.
Misfire happens across all 6 cylinders/not cylinder specific, not constantly, seems to happen more going uphill, so far;
New fuel pump
New spark plugs and wires
New dizzy cap and rotor
New PCV valve
Used FPR from an '01
Valves adjusted
Cleaned EGR port on manifold and block
Is it setting DTCs or does it just feel like its missing? Is there access to a scan tool with live data? I would be curious to see the EGR command vs EGR lift when its acting up.
In reply to logdog:
It's setting DTC, random misfire or specific cylinder misfire. Doesn't always trip the same cylinder or bank. Only have a code puller, doesn't give me a live data read. I'll see if he can get his hands on one.
Really weird, but I've seen Hondas with dented oil pans (constricting the pickup) throw this DTC and refuse to go over 4200rpm. If the oil pickup can't keep up when vtec crosses over then it is a failsafe.
Not sure how helpful these are as there's nothing about EGR and idk if the misfire was happening at the time this was taken. Says O2B1S1 and O2B1S2 fluctuates a lot with S1 going from .800+ to .00X and back, Sparkadv fluctuates between 9.5-10.5, Load % between 35-37.
Brand of plugs, wires, cap, and rotor? Cheap ignition parts can do that.
Looks like it's attempting to run lean, it's really rich, to start with based on the short and long term fuel adaptives. Clear out the adaptives and see if that fixes the lean out. If not, is the miss "hard" or "soft" hitting?
Its pulling a bunch of fuel. The fuel trims total out near 40%, and that's dead wrong. The two likely possibilities are the maf is over reporting, and the O2 sensor is correcting, or the O2 is reporting incorrectly, pulling fuel and causing a lean misfire.
Clear the memory, unplug the O2, and drive it. If it runs bad, the O2 is fine. If it runs well, it an o2 sensor. Don't buy a cheap one. OE or NTK is my choice.
^^^This. Those fuel trims are pulling a ton of fuel. Its almost certainly running very lean, and misfiring as a result. Though that would be unusual for both banks to be missing off one bad O2 sensor. It's possible there's two bad/ contaminated sensors. MAF or O2 sensors is exactly where you should be looking.
I have seen cars that are driven very short distances in the cold every day build up fuel in the oil, causing fuel trim readings like this due to fuel vapor entering the engine via the PCV. Its easy to tell, by clamping off the PCV line and watching the fuel trims. They would swing positive right away if this was the case. A oil change and a longer drive route would fix that situation.
Hello all, I'm the cousin in question. Thanks everyone for your help, I really appreciate it.
Some more backstory: I think the cause was bad fuel, but DuctTape&Bondo and I seafoamed the E36 M3 out of it recently and James Bonded the car behind us. Not to mention, I've put in a lot of Lucas FI treatment.
I've had the infamous "Honda hot soak" a few times. I don't do a lot of city driving or run errands so its hard to say that I actually have it since it affects MY2000 and they fixed it in 01. Honda's TSB says to replace the fuel pressure regulator (FPR) and the ECU (way too expensive). Others have reported swapping in the fuel rails and other parts from other Honda V6 engines. Problem is I haven't found MY 99+ Odysseys in the junkyard, and replacing the ECU is too $$$ of an option.
Kenny_McCormic wrote: Brand of plugs, wires, cap, and rotor? Cheap ignition parts can do that.
NGK plugs & wires, Hitachi cap & Back/Arnley rotor.
Ranger50 wrote: Looks like it's attempting to run lean, it's really rich, to start with based on the short and long term fuel adaptives. Clear out the adaptives and see if that fixes the lean out. If not, is the miss "hard" or "soft" hitting?
It used to run rich because sometimes I would smell a little fuel (dumping)...nowadays I don't smell it anymore so it might be running lean since it also struggles/hesitates going a slight uphill or with a/c on...Idk what adaptives or if the miss is "hard" or "soft" means.
Streetwiseguy wrote: Its pulling a bunch of fuel. The fuel trims total out near 40%, and that's dead wrong. The two likely possibilities are the maf is over reporting, and the O2 sensor is correcting, or the O2 is reporting incorrectly, pulling fuel and causing a lean misfire. Clear the memory, unplug the O2, and drive it. If it runs bad, the O2 is fine. If it runs well, it an o2 sensor. Don't buy a cheap one. OE or NTK is my choice.
I replaced the upstream O2 sensor with a Denso brand and it fixed it for a while. I was planning on buying another one for the downstream, but I think that has nothing to do with misfires or the way the car runs, just readings. I'm assuming I unplug the upstream sensor? I've looked in the FSM, and it doesn't say it has more than 1 upstream sensor, which is weird bc I thought there are suppose to be 1 for each bank of cylinders...I'll check the front of the engine just in case I missed it somehow, but I replaced the one on the exhaust pipe before the cat (which is closer to the firewall). I can post a pic/diagram for reference. Neither of which is on the headers or manifold.
TGMF wrote: ^^^This. Those fuel trims are pulling a ton of fuel. Its almost certainly running very lean, and misfiring as a result. Though that would be unusual for both banks to be missing off one bad O2 sensor. It's possible there's two bad/ contaminated sensors. MAF or O2 sensors is exactly where you should be looking. I have seen cars that are driven very short distances in the cold every day build up fuel in the oil, causing fuel trim readings like this due to fuel vapor entering the engine via the PCV. Its easy to tell, by clamping off the PCV line and watching the fuel trims. They would swing positive right away if this was the case. A oil change and a longer drive route would fix that situation.
I did an oil change just recently (<1k miles ago) and I didn't smell fuel in the used oil. I drive 20 miles one-way to work and sometimes drive 400 miles round trip once a month or so. I'm in SoCal so the coldest it gets in the morning is probably mid-50s.
I'm planning on cleaning out the MAP & TPS sensor, EGR valve, and the IACV next. But I think they are already as clean as they can be.
Hey Dave, welcome! Thanks for filling in the gaps, although I'm not sure about the bad gas theory. I filled up once while I was watching the car for you and it was still misfiring and smelling like gasoline. Could you have gotten some bad gas somewhere along the line and there's water or something in the tank? What does the fuel filter look like?
I know you replaced the distributor cap and rotor, could the distributor itself be bad? I know you don't want to keep throwing parts at it, I'm just talking out loud here.
How long did the new o2 sensor fix the problem before it came back? I know you had intervals of many miles where it was working fine then it would resurface.
BTW what specs did you adjust the valves to? some of the honda forums say that honda published incorrect specs originally...
In reply to DuctTape&Bondo:
Fuel filter looked good, at this point I think the fuel system is good.
I've retraced my steps, and thought about the valve clearance. I'm thinking maybe it was out of spec, but I set the intake to .008 inch. and the exhaust to .012 inch. FSM says intake is 0.008-0.009 inch., exhaust is 0.011-0.013 inch. (so I set it in between). I don't remember when exactly, but after I adjusted the valves, it ran fine for a while, but maybe the intake or exhaust valves became too tight and its choking up or something.
Distributor could be bad, but I don't hear about replacing the whole unit, just the cap & rotor.
I don't remember how long the o2 sensor fixed the problem....give or take a couple of weeks and hundreds of miles before it came back. At one point, I could've drove for 100 miles before it misfired, but recently (maybe bc of the colder weather?) it's starting to happen every time I drive it (20 miles one way trip).
This weekend I'm going to redo adjusting the valves. I've never heard of the specs being incorrect from factory, do you have the correct specs?
Idk if I mention this before, but before I was misfiring on cylinders 2,3,4 and random. Now I'm misfiring on all 6 cyl and random. So I've effectively made it worse by replacing parts 
In reply to Mine:
ah man that sucks.
The stuff I read about valve specs being incorrect applied mostly to CRVs but was linked to the Accord forums stating that many other Honda V6 motors from that period were affected. Don't have the specs, I'm at work now so I can't dig too deep.
Timing belt was something you and I discussed before too, being off a tooth might cause the symptoms you're experiencing, I know you had the TB done when you bought the car, but that was several years and about 80k miles ago, right?
I know at this point you're just done with it and not really interested in throwing more money at it. What will Craigslist give you for it?
In reply to DuctTape&Bondo:
Reason why I strongly believe its the valves now is because I've done almost all of the fixes for the typical conditions for a misfire. I would assume that the other conditions would make the car stall out, but she still chugs along, just hesitates a little. The fuel system should be clean because we poured half a bottle of Seafoam through the brake booster line & gas tank each. And as mentioned earlier, I've put half of a giant bottle of Lucas fuel treatment as well as filling up with Chevron/Shell for the past 6 months.
Timing belt was done 5yrs/70k miles ago. I'm due for smog + registration, but as long as I can pass smog, I'll just sell it before I re-register.
It's hard to say how much I can get for it. Most cars on CL are asking from $2500-$4500, but they're all I-4s in various conditions/trims. I'm shooting for $3500+ based off of cosmetic defects.
Hopefully along with the o2/maf suggestions above we'll get that old girl settled. Good luck and keep us posted!
**UPDATE
I adjusted the valves a little bit looser on Fri, drove it on Sat. but it still misfired. It drove a lot better, no hesitation/stumbling. I checked the codes and instead of all 6 cyl misfiring, now it was only 3. Adjusted the valves on those cylinders and drove to work today. 40 miles round trip and no misfire. 
I'm gonna give it til the end of the week (100+ miles) before I'll call it good.
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