Owner of a 2004 Escalade ESV, LQ9 Engine VIN N 6.0L Vortec, with 50 000 Miles on it, I have misfires at idle only.
Going through troubleshooting, cyl #2 is the offender cylinder. All tests have been done on this engine, except leak down test. I checked coils, injectors, spark plugs, plugs, intake gasket replaced, vaccum smoke test performed, PCM recalibration with J2534 device, MAF sensor cleaned, compression test done, see results in PSI:

CYLINDER PUFF 1 PUFF 2 PUFF 3 PUFF 4 PUFF 5 PUFF 6
2 116 148 165 177 183 190
4 120 153 173 185 195 200
6 115 152 173 186 193 202
8 83 123 155 172 182 190
1 81 128 156 174 183 191
3 81 133 158 176 188 198
5 105 148 172 189 199 206
7 110 150 174 187 196 200

So no issue to report on compression test, vaccum is around 19 inch Hg, so good also.

I made many measurements with the picoscope to analyze the pressure waveform into the cylinders, and seems like intake valve on cyl#2 is leaking.

As I need to remove the heads and replace valves, I would appreciate any recommandations on which parts I could install to get better performance on the LQ9 engine; any suggestion on rocker arms, valves, springs? Camshaft?
Street application only.

Thanks!

 

I would swap coil packs from side to side and swap wires as well and see if it goes to the other side. Also check valve springs.