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!
Could this be a bad ground or bcm? My PCM was replaced around 30k miles due to a broken pin on the connector. I was thinking it might be a bad injector because I ran e85 on the stock injectors causing the IDC to go to about 130%. I had a p0300 code a few times but I only notice a a misfire under 2000 rpm's in park or neutral. The truck runs normal and has full power most of the time but it's these random moments that it acts goofy.
Thanx for the tips troll bot
Originally Posted by erictuner
Look at ECT and IAT sensors which index some spark tables.
Flaky connectors can act like this.
Log all of your spark retard and advance component PIDs
and you can see which one was pulling. If you see indicated
timing pull back and none of the sub-components matches,
you might be seeing just bogus frame data. If the motor
follows (jerks?) though then it's real.