How to Diagnose and Fix P0302 Cylinder 2 Misfire on Honda V6 Engine

Intro Welcome to Professor's Garage! When the check engine light appears, what's going on? Perhaps you also noticed your engine is running rough, has some loss of power, more excessive fuel consumption, and perhaps you smell fuel from the exhaust. With an OBD2 scanner, you can run a scan and now it says: > P0302 Cylinder 2 Misfire Perhaps the code is anything from P0301 through P0308, depending on the cylinder number having misfires. The last digit of P030[2] means the misfire is associated with the cylinder number 2. And on this Honda V6 engine, this is the cylinder in the back, next to the firewall. Today we are going to find the culprit of the misfires and fix the issue. ## Analysis Let's start with an analysis. A P0302 or a related code indicates the engine failed to ignite the air/fuel mixture for a number of times in that cylinder and the most common cause is either: 1. A faulty spark plug, or 2. A faulty ignition coil pack; There are other possible causes, which I will discuss at the end. But for now, we will focus on these top 2 causes and hopefully get it fixed today. ## Test Now that ONLY cylinder 2 has an issue with P0302, let's find out whether it is the spark plug or the coil pack by swapping that coil pack in question with another on a cylinder that's working without any problem/code. For example, cylinder number 5 in the front is easy to access and has no misfire. So unplug the connector, unscrew it and take it out. We know this is a good coil pack so don't misplace it. Next, take out the coil pack on cylinder 2. It is in the back and you may have to feel it when taking it out. Now, we swap the two coil packs by putting the coil pack number 2 to cylinder number 4, and number 5 coil pack to cylinder number Again, secure them with the screws and re-plug the connectors. Before we scan the system again with a running engine, we should clear the existing code. With a Honda, this means, with the OBD scanner plugged in, you turn the key to On but do not start. And then follow on-screen instructions to clear code. Many part stores can do that for you if you don't have a scanner. Some people disconnect the battery to clear code but you will have to reset everything. So this is the last thing I'd recommend. ## Result and Fix Now the code is removed, start the car and scan the engine with the scanner again. If the code comes back saying: > P0305 cylinder 5 misfires Then it means the problem has moved to cylinder 5 and it's due to the coil pack we swapped from cylinder 2. In this case, replace it with a new ignition coil pack and the engine should run like new. I strongly recommend getting a replacement from Honda or an OE quality source. But if the code comes back with an unchanged misfire code: > P0302 cylinder 2 misfires Then the coil is not the culprit, and it is most likely the spark plug in cylinder 2. And we are going to take it out and replace it. If it's the first time you take out a spark plug, you may practice it with a cylinder in the front. Cylinder number 2 on this engine is in the back and harder to access. But with a spark plug socket (size ? with magnet) and a ratchet, it is not that difficult to take it out. Now the problematic spark plug is out, you may see signs of carbon deposits. Putting that aside, we need a replacement and I'd again recommend getting a new spark plug from Honda or an OE brand such as NGK or Denso. You cannot go wrong with these. Think about how long the original plugs have lasted and the peace of mind they will give you down the road if you continue with the same quality. Normally we can get a pre-gaped plug for your vehicle so you don't have to do it. And most often they are greased and it's NOT recommended to put anti-seize on the thread. You may overtorque it if you do and that can get you into bigger troubles. Thread the plug on with fingers and then torque it to 13 ft-lb on this engine. Or only hand tight with a small ratchet. Again, do NOT over-tighten it. Clear the code again and have a test drive. If the code doesn't come back, you are all done! ## Notes If the spark plugs are all factory plugs and one starts to go out, it's a good time to replace them all. Bad spark plugs will increase the stress on other components such as coil packs, which are more expensive. The interval of replacement depends on the vehicle but, in general, spark plugs rarely go beyond 100k miles. As for other causes of misfire, they can be due to bad fuel or faulty fuel injection, engine lubrication problems and oil getting into the combustion chamber, and perhaps other more costly reasons. So if nothing else, check/change engine oil and test the car with better quality fuel. Hopefully it is nothing more complicated. ## Closing I hope this video is helpful and informative. Consider give us a like and subscribe! If a professor (with a injured hand) can do it, you can do it. Until the next time, may the Lord bless you and give you Peace!