Help with a weird misfire

[briglicon]

I have a 1997 S10 with swapped to an LQ4, 243 P&P heads, shorty headers, 2.5" true dual exhaust, elgin E-1838-P (.560" lifts, 216/220 114 LSA), cold air intake. I feel a constant misfire at idle and through the lower RPM ranges, but no codes, no misfires show in the counters in the VCM scanner or my Snap-on scanner. And not a "hard" misfire, either. Just a constant vibration like maybe one cylinder just isn't keeping up with the others. A little background: This truck had a L59 with a cam and 706 heads before. The truck worked beautifully. I built this 6.0L and basically swapped the long block. At first I didn't pay much attention to the little roughness because the L59 kind of behaved like this until I got the tune right. I have the engine broken in and actually tuned with a wideband today. I used the high and low octane spark tables from a Z06 (since it's sort of a similar setup and my other timing table was kind of radical) I got my MAF and VE errors to where they are close, but noticed that the misfire feel didn't get any better. so I stopped tuning and started checking things. I found two coils were acting a little weird, so I changed them... no change. Checked all the wires, connectors, ect. Nothing out of place of making poor connections. I do notice a little lifter noise right around the 2000 RPM area, but my old engine literally sounded the same and these are new lifters, the preload is just past 1 1/4 turns on the rocker bolts. I attached the last adjustments I made to the tune, and the log file from right before. Any help or places to check would be greatly appreciated.

[chris35moto]

Would be curious to see the wideband readings. Are you using your o2 sensors? Bank 2 Sensor 1 looks like its dying.

[kingtal0n]

too much timing will make low rpm stutter/misfire feeling

make sure idle is low enough timing (~12* for stock cams) the factory uses like 17 or 18 in some tune files.. causes a idle misfire

[LSandlteditor]

Did you check the spark plugs? Sometimes its the simple things that get overlooked. Usually LS coils do not go bad. I personally have never seen them in all my years messing with them. Check the spark plugs

[briglicon]

Sorry for the long delay, guys. I literally got so busy at the shop that I forgot about this thread. Just in case anyone else searches for this topic I figured I would post what fixed my problem: I had a leaking intake manifold gasket on the passenger side. Turns out that you should spray WD40 or wipe a thin film of oil on the heads when installing the intake. When the surfaces are perfectly clean and dry, the manifold gaskets can roll the rubber over just enough to cause several small leaks. Pulled the intake, changed the gaskets, used the WD40 trick, and the truck has been running solid since then. Thanks to all of you that responded. My apologies.