Intermittent misfire Replaced coil, plugs, and wires still has intermittent misfire at normal city cruising speed

Check your coil packs and plug wires if applicable it could have just the sparkplug boots if so replace them. Chevy's are notorious for them prematurely wearing out from time to time.

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The engine may be misfiring. I had a 2.4L engine that did that and at long last I discovered that the "Coil Cover Housing" needed to be replaced. This is because the coil cover housing has the spark plug wires molded into the plastic as part of its design. For me this caused an intermittent misfire in one of the cylinders.

harbor freight sells cheap inline spark checker, good for checking wires/spark visually

Yes they are relearned within a or days of mixed freeway, city and stop and go traffic driving.

Vss (vehicle speed sensor) could be bad

sounds as if you need to be sure plugs are not fowling out and be sure fire from dist and coil is ok.

Cylinder 4. Each cylinder has it's own coil above the sparkplug.
If you have a misfire, it's probably a bad coil. But if it's an intermittent misfire, it may be the wiring to the coil. If it's intermittent, start the car and wiggle the wires to that coil. If you cause a misfire you need to check the wiring to the coil.
Goode luck.

A misfire can be related to a number of causes. Since the coil and spark plug were replaced and it did not solve this issue, it is most likely related to the circuit for the number 8 cylinder. A thorough inspection of the electrical circuit is what is required next. Also, engine compression will need to be tested on that cylinder as well as cylinder number 6 that is next to it. Vacuum leak around the intake port of the number 8 cylinder could also be a cause and will need to be checked.

cruise control operation is reliant on the following
road speed sensor ( speedo or VSS sensor )
engine rpms tacho/ ignition coil/module problem
clutch pedal sensor (VSS in automatic )
gear selection position sensor ( not properly adjusted causing flickering of the selector light)
brake pedal sensor
bad ground wire connections
r all need to work together or the CC will stop working
nothing to do with vents and all that you mentioned.
wire connections and harness connections for the transmission are suspect
CC will not operate under certain engine rpms and road speed

im a tech in the bronx and i dealt with the same code for the misfire. burt i realized that there wasnt any power to the coil of #2 cylinder. I replaced the sensor mounted on top of the air filter box, which solved this problem.