Bad Misfire Problem

[Sylar]

So three days ago I started getting misfire on heavier throttle. Then yesterday it started misfiring worse, then to the point where it would misfire under very little throttle and even idle. I ran the code on Sunday and it said misfire on cylinder 2, then ran it again today and I now have three, misfire on cylinder 1, 2 and 4. I thought it may have been a bad valve cover gasket at first, but took the plugs out and no oil in any of the wells or on the plugs. I also noticed the misfire gets much worse once the car is warmed up.

Edit: Ended up being a bad coil, should have checked that first but I was stupid and didn't.

[imnuts]

Vacuum leak or post-MAF intake leak. Does it run better if you unplug the MAF?

Sent from my Moto X

[Sylar]

Well I found out the suction pump was broken in half and leaking, assuming that was the problem I replaced it, only to find out that wasn't the problem. Now I'm getting four codes, P0300, P0302, P0304 and P0171. I tried unplugging the MAF and nothing changed. Another problem that may be related but not sure, I replaced my fuel pump a few weeks back because my car would have trouble starting (only to find out the problem was actually the coolant temp sensor), and it's been making a lot of noise, very loud humming/buzzing sound in random patterns. My old fuel pump would do this too.
At this point I'm clueless, I'm going to check the fuel pressure tomorrow to see if it may be related.

[old guy]

Have you replaced the fuel filter? the fuel filter also serves as the fuel pressure regulator. The buzzing sound may be coming from the filter rather than the fuel pump.

[JQADDINGMACHINE]

My car had the high pitched humming noise from the passenger rear area and would misfire at full boost. replacing the fuel filter got rid of the noise and the misfire.

[Sylar]

Well I still don't know what's causing this issue. I replaced the O2 sensor, still have the problem. I checked the fuel pressure and it's right around 58 psi, and from what I understand, is normal, so that leads me to believe it isn't being caused by the fuel filter since it's getting the proper amount of pressure. I'm running out of ideas on what it could be. I don't think it's the coils or injectors, because it's misfiring on three different cylinders, and the chances of all three going bad at once seems unlikely.

Does anyone have any ideas on what might be the cause?

[diagnosticator]

Clear the fault codes, then swap the coilpacks from the cylinders that are misfiring to the opposite cylinder bank, and see if the misfiring cylinders fault codes follow the moved coilpacks/shift banks. IF the fault codes show different cylinders are misfiring after swapping the coilpacks, that will prove the coilpacks are faulty. If the misfiring cylinders don't change, then there is something else causing the misfires.

Troubleshooting problems means checking all the possible causes for a symptom, in order of most likely to least likely occurring, until the cause is found. It doesn't help to second guess or assume anything.

[Sylar]

Yeah, we did that and it ended up following it, went up to Advance and got a new coil. Problem fixed! Should have been the first thing I tried, but once it started showing misfire on different cylinders I started to think that wasn't the problem.