So, I recently removed the Displacement on demand from my G8 and added a LS9 cam in preparation for a supercharger later this summer.
While tuning for the new cam and DoD delete I can't seem to find out why I am having a lean spike only while cruising with slight deceleration. I have tuned the MAF and disabled VE but no change. I then disabled MAF and checked VE. No change with VE only and the trims looked good. I re-enabled both MAF and VE but the spike remains. It seems to be a random occurrence. It does not happen every time I decelerate and its unpredictable but it only happens during deceleration while cruising. I disabled DFCO to try and eliminate that and there was no change. Sometimes the spike will be accompanied by some slight bucking. I thought it might be something to do with the Torque converter engaging. I used the VCM scanner to lock the converter and that kind of made a change but the lean spike turned to a rich spike. So then I unlocked it but that didn't make a change.
I have a scan from today. its about 20 minutes long and the spike occurs multiple times during the scan. I just cant figure out what is causing my problem. Is it a mechanical issue or a tuning issue? I thought it was an exhaust leak at first so I got new manifold gaskets and resealed the manifold to the cat. Maybe it is timing chain slack? Idk guys, I need help.
2009.5 Pontiac G8 GT 6.0 L76 A6
Mods: Vararam OTR intake, LS7 MAF, DoD delete, LS9 Cam, .660 Valve springs, HD chain, melling Oil pump, Pypes axle back mufflers
G8 3.0 DCFCO disabled LS7 MAF+Timing+LS9 cam O2 B1S2 off PE 12.5afr.hptlean spike problem 4-17-17.hpl