Hello, I did a 6.2 swap in my 5.3 Yukon. I have a cam motion VVT cam. I have the cam phaser installed with the block off, the most it will get is 8 degrees of retard. I have a few thousand miles with many WOT passes with no issues until this week.
Recently, WOT has been breaking up. I will punch it in 1st gear, it will fall on it's face, then keep pulling. It's random at what RPM it happens at, sometimes it's immediate and sometimes it happens up at high rpm. I swapped plug wires and that didn't do anything.
I figured I would just turn VVT off (no retard) and see what happens. It was an immediate clean pull. I have attached two logs and my tune, anyone have any idea where to even begin looking? I am about to throw a 3 bolt cam in and be done with it.
In the bad log, at time 53.973 seconds, you can see as soon as VVT activates, the RPM drops a bit. I felt it as it happened.
There is another WOT later in the log and at 5:07 you can see it hit 6500 rpms, then hit a brick wall and drop all the way down to around 6200. This was not just the shift, as the timing was still fully in at 25 degrees.
The good log shows no RPM drop anywhere and feels clean all the way through.
So one thing that was different than normal is I ran an entire week with E85. No idea if that gunked something up, but I mixed in 10 gallons of 93 just now and drove it a good bit. Now it's pulling smoothly again.
Wanted to update in case someone searches for a similar issue. It has nothing to do with VVT.
I believe it's just the TCS/Stability control. Apparently very aggressive in the trucks. I was able to catch the electronic TPS % going down even when the accel pedal % was 100% and even with tcs and stabiltrak OFF.
My theory as to why it was worse with E85 is because likely the truck makes a good bit more torque on E85, so it was triggering the event.
In the tune I turned off spark control for TCS and left it at ETC only, so it's less jarring. I guess if I want full power, I need to pull the ABS fuse.
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