Ignition abruptly retards then advances under part throttle.
I've been trying to figure this issue out for the past few months and keep coming up short. I have a 2008 Chevy Colorado 3.7L i5 and every once in a while, under part throttle, the ignition retards to the extreme then goes back to the desired advance for a split second then retards again. This continues until I shut the engine off and restart it but sometimes it takes a few restarts to get it back to normal operation. I replaced the exhaust cam actuator solenoid thinking that was the cause but it was not. The problem with this is that it happens randomly and the chances of catching it on my scanner are slim. Your thoughts are much appreciated!