Spark advance and knock retard problem

[Gregs]

I've been having this weird issue. As i'm driving down the road at constant load, rpm, tp, etc. All of the sudden i'll drop from lets say 29* to 16* instantly and then right back up to 29*. when it brings the spark advance up at that rate it causes knock retard of like 3-5*. what gets me is that there is no load or tp change or anything else. Where should i look in my tune to figure this out? i do have a log for an example, please forgive the few extra pids i have selected i keep forgetting to remove them from the bbl settings. the advance goes from 28.5* at frame 340 and 16* at frame 341. it knocks when it brings advance up from 16*

[odd boy]

check the crank pulley, if it is shaking it would cause the timing fluctuation.

[Gregs]

check the crank pulley, if it is shaking it would cause the timing fluctuation.

thanks, i'll check it out and report back...i hope its not loose, thats a little worrisome.

[MSURacing]

Are you sure it is not the AC clutch kicking in or out? That causes the spark to do that. As for the knock, are you in lean cruise? If so, that could be your knock.

[Gregs]

i think i have the ac off since its in the 30's here, but maybe it was still on. I am running lc but i've been having this problem going on long before that. I think the knock is from quickly adding 10*

[ScarabEpic22]

If you're running the defroster the AC will kick on, dont know if that could be part of the problem.

[Gregs]

i'll have to do some experimenting to see if its the ac. I looked around in the tune to see if there was some spark ramp in rate that i could adjust for the ac but i didn't see anything.

[joecar]

Log the EST_xxx_DMA pids to see if they give any clue.