Multiple misfires detected - no codes

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May 21, 2017
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Can someone explain me how does misfire detection works? I've been running live data with my Autel on both hondas (Pilot and Civic) and noticed that there are multiple misfires detected on various cylinders (all within minutes after engine startup). No DTC codes stored, never ever seen check engine light with almost 100K miles accumulated on both vehicles. See below the screencap of the report from each vehicle. My understanding was if there was misfire detected it'd throw a code and store it in the memory. Also, what could be the cause of them misfires?

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The misfires have to happen for a longer period of time or more often for a code set. Some causes:spark plugs, coils, wires if you have them and a lean miss from a fuel delivery problem or vacuum leaks. Low compression would be the least common but most serious cause.

I had a misfire but would not set a code because it didn't happen long enough. I had to go onto an isolated road and really work the engine till the code finally was set for a particular cylinder.
 
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Is there anything I should be doing about this? Both cars drive just as they did on a day one so i'm not sure how long have these misfires have been happening. I am puzzled
 
Do you fill them up at the same gas stations? Maybe you got some bad gas. Some misfires won't trigger a check engine light if the O2 sensors are reading acceptable values.
 
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Both cars are exclusively on Costco gasoline (same location), both are on Regular supposedly top tier.
 
Personally if it were me I'd change gas stations and see if the situation improves. Has the maintenance been kept up on both cars?
 
Yes, both cars are very well taken care of as far as the maintenance goes (all fluids). I've done multiple UOA as well on both with good results. Cars are fairly new (‘16 and ‘17) with 40K and 47K on the clock
 
Some would suggest an intake system cleaning if the engines are direct injection. I haven't heard of any issues with Honda's direct injection so I doubt it's carbon buildup. Try a different gas station and see if it improves. I'm not a fan of Costco gas personally. They mix the additives on site at most locations I think. What happens if that mixing device isn't working properly? I think Costco claims to add the most additive out all the US fuel retailers iirc. At what point does too much additive interfere with combustion? Who knows lol. Oh of my buddies pumps Costco he in all his cars and trucks exclusively and I'm not a fan of how his engines idle. Sorry, end rant!
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Dirty injectors could cause that, I'd try a couple of rounds of good PEA injector cleaner. Had the same type small misfire count on 2010 Sienna, V6, took a few rounds to clean up but the count is back to zero. I should note I cleaned the throttle body and changed the spark plugs, but I wouldn't think you would have to go that far yet. And I would doubt your vehicles would have a vacuum leak being they are relatively new.
 
Any particular injector cleaner brand you'd recommend? I'm totally new to the cleaners, never used them really
 
It's not bad gas.

All of the misfires detected are within minutes after cold start. The engine is in open loop. The ECM's goal when first started is to get the engine(and catalyst) up to temp as fast as possible. As the engine warms the ECM is going nuts adjusting fuel curves and timing.
I can plug my Snap-On Solus Edge Scan tool into every one of my vehicles (well, not my Willys) and likely see the same cold instantaneous data.
Drive them and they will be fine. IMO, there is nothing to see here.
 
Originally Posted by Zaedock
It's not bad gas.

All of the misfires detected are within minutes after cold start. The engine is in open loop. The ECM's goal when first started is to get the engine(and catalyst) up to temp as fast as possible. As the engine warms the ECM is going nuts adjusting fuel curves and timing.
I can plug my Snap-On Solus Edge Scan tool into every one of my vehicles (well, not my Willys) and likely see the same cold instantaneous data.
Drive them and they will be fine. IMO, there is nothing to see here.


Hmm, the only time I've ever seen misfires on my vehicles on the misfire counter on cold start was when one of my vehicles had a fuel injector that was bad. Your engine shouldn't be misfiring to warm up the catalyst.
 
Originally Posted by parshisa
Any particular injector cleaner brand you'd recommend? I'm totally new to the cleaners, never used them really


Redline SI-1 is good. They actually sell it at Pep Boys (they don't carry Redline's full line, and you can't get their oil at PB)
Chevron Techron is good
Another popular choice is Gumout Regane (look for the ones that say PEA on it)

Whatever brand you buy, add it when the tank is almost empty.
 
thanks guys, appreciate everyone's feedback. ordered some techron, will add and see what happens. although, if there are more opinions or suggestions - please keep them coming
 
Just to clarify the misfire count is because the computer sees an imbalance, and that could be spark, vacuum or fuel delivery, although a head gasket leak may also be a possibility.
 
It just doesn't make sense how can any of these may arise on a low mileage vehicle maintained meticulously and driven very reasonable? And really 0 performance decline can be detected...don't know
 
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