[16ssFR]

Mods: LT2 manifold, Roto Fab CAI, Headers, X pipe , DSX Flex Fuel Sensor, and Tune.
Has new spark plugs and wires. Also tried moving around wires and spark plugs but no luck.

The misfire only happens on E85 and when I pump 93, it goes away. Checked logs on scan tool and only happens on cold start at arounf 1,200 RPM. Seems to be only happening on cylinder 2. Cylinders 4, and 8 have maybe 10 misfires but hundreds on cylinder 2.

During tune logs, Throttle body would open 56% at WOT. Saw in another forum that having a stock 87mm TB may cause the issue. Ordered a 95mm TB but want to get some feedback.

Any help would be really appreciated.

[cjperformance]

E85 is harder to ignite esp cold. Thats one reason they still add 15% gasoline. Maybe weak coil on that cyl?

[KingLT1]

Is it misfiring enough to trigger a CEL or you are just seeing some misfires in the log? Because it's pretty normal to get some cold start misfires on E85. Part of the reason why they drop the E content down in the winter months. E likes heat and doesn't like cold.

[ctrlz]

Originally Posted by cjperformance

Maybe weak coil on that cyl?

Good first idea!
try swapping it to other side. If not spark problem, then take a look at fuel trims.

[cmitchell17]

Originally Posted by 16ssFR

Mods: LT2 manifold, Roto Fab CAI, Headers, X pipe , DSX Flex Fuel Sensor, and Tune.
Has new spark plugs and wires. Also tried moving around wires and spark plugs but no luck.

The misfire only happens on E85 and when I pump 93, it goes away. Checked logs on scan tool and only happens on cold start at arounf 1,200 RPM. Seems to be only happening on cylinder 2. Cylinders 4, and 8 have maybe 10 misfires but hundreds on cylinder 2.

During tune logs, Throttle body would open 56% at WOT. Saw in another forum that having a stock 87mm TB may cause the issue. Ordered a 95mm TB but want to get some feedback.

Any help would be really appreciated.

Did you change the spark plugs and wires after the misfires started happening? Or they started happening after you changed the plugs and wires? If so I would double and triple check the wires are all seated and that you didn't crack a insulator and spark is leaking. Also are they iridium tip? If you even touch the inside of an iridium tip plug with metal it will cause a misfire, that's why they tell you not to try to check or set the gap on them.

It is a random misfire code? or is the check engine light continuously flashing?