Random misfire?
 

My friend has an 05 civic EX that he needs some help in diagnosing. Originally, the only thing he noticed was a check engine light, didn't notice any other problems. I scanned it for him and the only code that came up was for a cylinder 1 misfire. I cleared the code to see if it would come back. I'm assuming it came back fairly quickly. Yesterday I went over to see him and he said his car had gotten worse. He said was driving on the freeway and could feel a definate misfire when cruising 2-3K rpms. We checked it out a little last night. He said he put new spark plugs in last oil change, about 5K ago. But we pulled out the 1 and 4 plugs and they looked fine. Also made sure all coils were pushed all the way down. I didn't have my scan tool with me to check if the code was only for cylinder 1 still or if other cylinders were misfiring too. The runs and idles fine but if he holds it around 2-3K rpms you can hear it miss randomly. So, before he goes out and spends money on a new coil and/or fuel injector only to not have it fix the problem, I was just curious if this was a common problem to these cars that you guys could pinpoint right away.

Also, he just got a new job this week requiring reliable transportation, so we're trying to get this fixed ASAP. The car has about 67K miles and has an injen short ram and greddy exhaust btw. Thanks in advance for any help!

Re: Random misfire?
 

You need your scan tool. Clear the DTC between each test. Listen for the click of the injector (I use a screwdriver, tip to injector and handle to ear). One at a time, exchange the coil and spark plug and see if it's still misfiring at the same cylinder. If it's now misfiring in the cylinder you just exchanged the coil or plug in, then that coil or plug is bad. Also check fuel pressure and valve clearance.