2014 v6 engine miss

At 47k I’ve developed an engine miss. It started out seeming like the idle was a bit high, maybe 750 rpm. My truck sits a lot, so I put some fuel system cleaner in the tank. Very soon, the engine dropped to around 600 rpm and seemed better. With a full tank with fuel system cleaner in the tank, I drove it 300 miles followed by another 300 mile trip but it hasn’t cleared.

I notice it only at idle, it stumbles, more like a twitch, and I see the tach dip. The plugs are DENSO iridium’s with about 10k on them. I haven’t gone any deeper yet. Any suggestions? No CEL to read.

 

I had a mysterious mis-fire condition in my truck a few years back, maybe 125k or so. Would only happen in drive at a stop light. Only threw a code twice during mis-fire incident but was still hard to diagnosis. My root cause was a bad denso coil pack. I replaced spark plugs as a starting point. got better fuel. cleaned maf. unplugged battery and cleared fuel trim values to re-learn. Finally bought 1 new coil pack and swapped cylinders till it went away.

 

I confirmed that the plugs have 20k on them, Denso Iridium's. I pulled and cleaned the MAF sensor, no change.

the truck continues to run fine with no miss under acceleration, only at idle. I listened to the exhaust today and it’s worse than I thought. I may resort to a new coil pack and swap it a cylinder at a time as suggested. I

I have no codes at this point. I have a cheap $40 code scanner, of course it doesn’t show what I need to see. If I found a friend with a professional code scanner, is this something that would show up?

 

I changed my plugs with the Denso Iridium bought on Amazon. Site said they worked on my 2014 V6. About 10k on them one morning, developed skipping. Not thinking it was plugs but something worse, got the truck to the dealer and found those plugs not to match factory Denso Iridium. Side by side comparison, a bit different in size. Dealer installed new, factory plugs. Going forward, I go to dealer for parts. By chance, did you purchase those plugs from a non-dealer source?

 

Good catch, I was going to suggest if u had ur old plugs to try them, it's free.

 

Assuming it's the V6, I would try switching out the plugs for the correct copper ones and see if that helps.

 

There are You Tube videos showing that a lot of stuff from Amazon and E-Bay are counterfeit even though they appear to come in proper packaging. It will cost you, but we should only buy from dealers to be sure it is original.

 

My money's on counterfeit spark plug.