Rep Power: 0

My 2000 Honda Civic (stick shift) recently had this problem. I had just replaced a faulty crank shaft sensor as well changed out all 4 of my spark plugs so I have no clue. The car would run fine after a straight cold start but after 20-25 minutes it would start acting all weird. The RPM’s would fluctuate as well hesitate when the car is in gear as I drive. It’s clear that they’re misfires but no source of from where. There would most time where the car would stall out during an idle or even when I Cruise the car in neutral. I did a scan for the check engine light but all it reads is a bad speed sensor and misfire in any cylinders. Could a bad speed sensor cause misfires and the way how my car is acting right now?

 
Rep Power: 511

Nah, speed sensor and misfires are independent of each other. Speed sensor literally just read wheel speed at the.. cv joint.. ish.. Average it all together (i'm assuming, at least) and there's your speedo readout. Misfires can be caused by a plethora of things. Bad ignition coil(s), bad wires, bad plugs, injectors, compression issues, the list goes on.

 
Rep Power: 210

Try a coil spark/arc test by using a long screw driver that is grounded to the chassis and see how far coil spark will arc to the grounded screwdriver's (flathead) tip during cranking. Keep gas pedal to floor during cranking to shut off the fuel injectors.

Start with the screw driver tip an inch away from the coil and slowly move it towards the coil noting arc/spark strength and distance. I used one side of battery jumper cables to connect chassis ground to screwdriver. A strong coil should arc/spark an inch. A weak coil will most likely die during this test but that is good because that's the issue anyway. If it needs a new coil only use a Honda oem coil.

 
Rep Power: 511

Or pull the fuel injector fuse. lol