Hi All. Like others I was getting the dreaded misfire codes for all 6 cylinders AND a random misfire. I checked for vacuum leaks, changed the plug, checked the EGR and read the live data for fuel trims etc. I was convinced it was the coils. To test I bought ONE new coil and put in Cylinder #1. Reset codes, drove and still got all 7 misfires. I moved the new coil to Cylinder #2, then 3,4,5,6 each time resetting codes. I always got the same 7 misfires. Clearly not the coils...right? So I read live data again and still thought it couldn't be anything but the coils. Bought 5 more coils, replacing them all..reset the codes and guess what? No misfire codes? WTH? Passed inspection...all is good. Except...at idle....occasionally...you will still feel a miss, or stumble like bump, bump bump. When it does this the tach is still steady. live data only shows a small 40 rpm sway in idle not shown by tach and not related to this miss or stumble. In the 2500 miles I've driven since the coils I did get a O2SB2S1 and O2SB1S2 code and replaced those two. Live data does not have car running rich or lean. Fuel trims do not expose a vacuum leak etc. Anyone care to guess what that miss or stumble is? My only guess is I have a bad or clogged injector...thanks for any ideas

 

Where are your fuel trims at when the engine is in closed loop and idling? What happens to the fuel trims when you hit the gas pedal?

 

Thanks for replying !!! My Short Term fuel trims closed at idle are pretty much 0. They may go +/- 1 and not together. So Bank 1 may be +1 and Bank 2 may be -1.. Long terms are basically the same. When I hit the gas pedal the short terms rise and then come down as I ease off pedal though they bounce up and down before they settle down. Never have I seen a long term over 10% My O2S are The front ones, which are really air fuels are flat lines B1S1 High 0.000 Current -0.031 Low -0.129 B2S1 High 0.000 Current 0.000 Low -0.086 The Rears have a normal wave pattern B1S2 High 0.720 Current 0.670 Low 0.080 B2S2 High 0.730 Current 0.480 Low 0.075 Let me know where else to look Right now I'm thinking of replacing all the injectors. I still haven't figured out why replacing all the coils worked :-)

 

How many miles are on the engine? Have the valves been adjusted?

 

200K....Not by me. I got car for FREE because owner was quoted huge prices to deal with the 7 misfire codes. First thing I did was check compression, which was surprisingly very good and less than 5% between cylinders. I then did coils which removed codes. I still have no CEL or codes, just that irritating stutter which does not appear on cars tach or in live data. Now I am not dealing with an expensive data reader so the refresh rate may disguise some things. I just went for another long ride. Again the O2S look like I described above. The post cat readings to me look normal. The fuel trims again...are tiny. Almost always under 6% generally down near zero. If I accelerate from stop they appear to go up then down..if I'm cruising at 55 and go to pass they decline. But again we're talking single digit numbers. Long term fuel trims live between 0 and 3%. I thought about valve adjustment and probably should do one just to know its done but I'm skeptical that is it simply because if a valve is loose (or tight) it's always that way. This car can go a day or two without doing this miss feeling then it may do it once or twice, then some days it does it a lot. I honestly thought I had bad gas. Put in Seafoam and drove it till tank was almost dry. Still have problem, though maybe not as frequent. Baffling (to me)

 

You might want to clean the EGR ports in the intake. Ignore my post in the thread below and follow RedBull's advice.

https://www.hondaaccordforum.com/for...ages-v6-36169/

 

Funny you say that...I just completed it a few hours ago. Was not really clogged (now it shines) but sadly had no effect

 

Do you get the shudder randomly, or does it happen at a certain rpm, accelerating/decelerating? Can you scanner read pending codes?

 

Completely random...generally felt most at idle. You can sit at 10 lights and its as smooth as silk Then the 11th light your get that miss or stumble yet the tach rpm doesn't flinch car doesn't shake but its very noticeable. On the live data, which I guess is more accurate that the gauges...the rpm fluctuates at idle...even while not stumbling..by maybe 30-60rpm (if thats any clue) You cannot force car to do this (which is frustrating) If it starts the miss or stumble (not sure what to call it) and you floor it you still accelerate nice and smooth. No stumble, no loss of power, no exhaust popping etc. Very weird. My last guess is to replace the injectors

 

I'm not a fan of replacing parts blindly. I remember sending my injectors from my 95 accord to be cleaned and balanced after 13 years. The before was not much different than the after.

I would guess a clogged injector would cause problems all the time and not 1 out of 11.

Does your scan tool have a misfire counter for each cylinder?