Quark 80b and hacker c40 motors

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Or shutting off or lowering the LVC via programming?

Are the motors new or used? A demagnetized motor will cog like crazy until something burns up.

What happens if the throttle is applied while the car is in the air? (no load)

Good connectors are necessary for the battery to esc connection as well. One bad solder joint anyhere will cause problems.

IMO the 5l is too much motor for that esc. It wouldn't cause the cogging, but that motor can pull more amps than the esc is capable of. If you get it running watch temps closely.