Originally Posted by
rhinogt
Ok guys and gals I need some assistance making sense of this. This week on two separate occasions I have gotten spark source = pre ignition. It starts at 6000 rpm on a wot pull. I haven't seen this before. Mind you in between these pulls I have had wot pulls that don't show it, and this has all been on the same tank of gas. When it has done it, I'm only getting 22-23 degrees of timing but no knock activity. Typically at 6000 I am seeing about 26-26.5 degrees with negative knock retard. I have changed nothing in that area of the tune in quite some time so I'm kinda lost for words. The only thing really different was I enabled flex fuel. However all this has happened on 93. I just switched over to e85 today and it appears to be gone.
Could it all have been bad gas?
Even though some of the time it allowed me full timing?
What causes the car to go into the pre ignition timing mode?