What is causing this erratic spark?

[realspeeddan]

I've got a 2011 Corvette on the dyno.

It has a GM "stage 2" cam according to the customer, with stock cats and exhaust manifolds, and a Vararaam air intake. (Not my recommendation for a parts combination. Usually the corvettes I tune have long tubes if they have a large cam).


The tune is 98% done, but I get an erratic spark timing reading and a noticable shake to the car when at light to mid throttle at low rpm. Usually applying more throttle will smooth it out.

At first I just attributed to to big of a cam at too low of an rpm. But then I noticed that the spark timing is swinging wildly whenever the shake occurs.

I had already turned down the Burst Knock response and that smoothed out lot of stumbling. But there is still a persistant shake under certain conditions that is always associated with an erratic spark reading on the datalog.


A lot of the misfire monitors are turned off (32,798) to prevent problems with the stability control.