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Hello.
I am looking to get new coils for my new 6 liter as I get occasionally misfires(doesn't cause any backfires, rough running, etc) Moved current coils(original 255K) around, changing nothing. New wires and plugs.
2003 2500HD, 4.10 gears, 4L80, 4wd. It generally only shows up at or above 2500 rpms(which gets there pretty quick).
CompCam stage 2 truck with a large rpm ranged. This truck won't seem anything over 6K.
Truck runs perfect other than this. No codes, but original cats.
Any recommendations for coils. There are a lot out there.
Thanks
jeff
weak Valve Springs possible ? ?
Reports of bad/counterfeit spark plugs. Sure you have good parts ?
I'd replace the spark plugs first, NGK TR5 or TR55 and be DAMN certain they are genuine Japanese manufacture, gap 'em short: I'd go .040".
Usually when you do cam and/or converter you have to dumb down the misfire tables a little bit.
if you can’t feel the misfire I’d start there.
otherwise just about any oem coil will work. My favorite are the d581s because the plug wire connector is high and back but they also happen to be some of the strongest oem coils as well and don’t fire early like the d585s.
Not saying there's anything wrong with TR6 plugs, but that is COLD for stock compression street motor.
I use the TR6 on a 4.8L under a Magnuson TVS1900, and they work fine.
...... I use the TR5 on all my NA motors.
I agree with Full Power, some of the parts on Amazon & Ebay could be cheap Chinesium knock offs. I use the iridium ones for a iron LS3 6.0 liter with a mild Comp cam and they work fine.
Here's a link to check and compare if they are fake plugs. https://www.ngkntk.com/newsroom/blog/emea/fake-or-not/
Thanks for all the info! I'm going to pull one of the plugs and look at it as per the website posted.
Will check with my programmer and see if the misfires can be "dumbed down".
Will update this thread with any new info I get.
Thanks again,
jeff
So are the misfires random or directed to 1 cylinder? I'm sure a smaller truck cam wouldn't need the misfire table softened much if any, but hard to say whats going on. Is compression solid across the board? A TR6 won't give a bunch of problems (as long as its genuine) even if it's in a mild deal it's just not that cold, but probably not needed here. I stay away from the ebay/amazon plugs, fuel injectors etc etc unless it comes from a vendor you know that uses the platforms to sell.
agree with amazon crap plugs. couple weeks ago did plugs and wires for a friends wife on her 18 tahoe 5.3 ran fine before i changed em but was time to service anyway, she had all the parts...........put all together and ran like complete garbage. asked her what store they came from and yep AMAZON all 8 plugs for 31 bucks (acdelco stock) pulled the box and 1 plug took it to the local napa and they were really good fakes ,boxes even looked legit just slightly off color. so i put all new plugs and wires back in it blue beldan wires and acdelco plugs (you know real ones) and it ran like a champ. moral to story china can kiss my ***.........
I beileve that is #4. I don't believe so. Not sure about the oil. No hesitations, no burning, starts very fast, has plenty of power.
So, go up a heat range? What would be the part * for those guys?
Thanks
jeff
I would switch a injector from the offending side to the other side of the engine and see if fouling follows it. Another thing to check is the #4 cylinder valvetrain, pushrod, valve spring, rocker? Anything out of the ordinary.
I've attached a pic of one of my plugs so that you can compare. Greyish tan hue is what you're looking for.
just seeing the misfires(flashing engine).
I am posting a logfile from my scanner. It is when the car isn't fully warmed up, but the warmed up version is almost identical, except that the misfire come faster when its hot.
jeff
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Misfire on fresh 6 liter 
