Newbie needs help with datalog (eehack) review, LT1 surging idle

[TurboWalt]

Hi,
Newbie here needs help with surging idle on 95 RMS. I've checked for vacuum leaks to no avail. No CEL, only surges during closed loop. At this point I'm suspecting bad Opti. Can anyone review my eehack datalog below? Any help would be much appreciated.


Download from iCloud

https://1drv.ms/u/s!AlOqOsaYrouuhg73nl3PFFPPNusT

[steveo]

yeah if you graph your RPM you pretty much see a good example of what a screwed up engine position input looks like.

your RPM square waves to 5000rpm+ for single frames. it's impossible for your rotating assembly to accelerate so quickly, even if you were smashing the throttle (which you aren't, TPS remains at zero), also nothing else in the datastream at those points sees abnormal, so obviously whatever gives your RPM input is lying

in the case of an LT1 that'd be the opti lying

could also be something interfering with your opti signal such as a bad opti harness, but probably the opti itself.

your MAF has an error code too, even though it seems to be functional. probably because airflow is way too low for the RPM it reads during those spikes but who knows.

[TurboWalt]

Thank you, I'll try the harness first before pulling the opti.