A few days ago when driving my 2000 civic I felt as if something was slightly off. The Idle was a bit high and at times had sudden drops. I got home just fine, parked and watched the idle which had returned to normal. I turned off the car and tried to turn it back on. The engine cranked at normal speeds but didn't start, when I tried again this time the crank was slow and again no start. I tested the batter and it had 12v. The car was able to jump start very easily and ran fine. After jump starting, the car is able to start one or two times before returning to a slow crank with no start. I tested the voltage while the car is running and got 13.4v so i believe the alternator is running okay. Another issue the car has is a P0325 Knock sensor code. I tried putting in two new knock sensors and still there. got a new pig tail and rewired it to the ecu but code is still there. One thing that's odd is the code gets reset whenever the car goes into the slow crank phase. Whenever I jump start it, there's no CEL and after driving for a minute or so it comes back on. I've been looking everywhere but can't seem to find similar issues online. People mentioning to check the battery cables for corrosion, alternator, battery and grounds. The cables are fine, grounds are tight, the battery is pretty new and the alternator Is putting out voltage to the battery. I'm going to get the starter checked soon but most everywhere i read people say the starter is fine if the engine still cranks over. Does anyone have any advice on what else i could check or what could be causing the problem? Also I've never posted on the forums before so if anyone would like additional information please let me know. Thank you.

 

Update: Today as a sanity check I got the battery tested and turns out the battery was bad, everything runs good now. I was not aware a bad battery could cause symptoms like this. Even though it had a good voltage reading and was holding charge, I suppose this is the reason to also test the power (amperage) the battery puts out when cranking the engine. My guess is this test would have failed.

 

12v is not a good voltage. I'd look for 12.5 or higher. Also, voltage doesn't necessarily tell you about cranking power. And, it's good practice to put dielectric silicone grease on the terminals to prevent corrosion.