Ok so my son's 98 Civic LX auto 140k+ I got called and told his crank sensor had went bad , I guess it had thrown a code. And the car left him stranded. Long story short I'm fast forwarding to today. I replaced the CPS sensor and finished putting the car back together , and put a new harmonic balancer on due to he broke it trying to remove it. Again long story. But anyways we go to try to crank it and it wanted to the first rip but didn't. Had spark so I pulled the plugs and they were gas fouled. Assumed from him and his buddies trying to crank it repeatedly for long periods of time. I go and buy new plugs , gap em out and install. This time battery was dead. Forgot to mention that earlier. But we jump it off and it ran fine. 2 laps around the neighborhood and all good. Shut it off and no restart due to bad battery , do I bought a new battery and installed it and it started great. Back out of the driveway and we notice the rpm gauge is at like 3k but still at idle. It goes up when we tap the gas but came back to 3k so I told him to drive round the block and he stepped on the gas and it kinda stumbled and backfired through the intake. Forward and reverse gears it did it in a m