Cylinder 4 Misfire

[Dadunn536]

1999 Expedition, 5.4 engine, 170,000 miles.
While driving, started running rough.
No CEL, but Pending code P0304 (Cylinder 4 misfilre).
Replaced #4 COP and plug.
Still running rough and after driving a while, the CEL illuminated. Displayed P0304 DTC and P0136 (and O2 sensor circuit Bank 1 Sensor 2) pending code.
Since the P0136 is for one the #2 O2 sensor on bank 1, I’m guessing its related to the cylinder 4 misfire? Also, freeze frame shows "Fuelsys1 OL-Drive".
What, if anything can I discern from this?
Does this give me a clue as to whether the #4 fuel injector is working?

 

[Petesexpy]

Let me cut and paste here. BTW, you are killing your cats...

• Bad Spark Plugs– Spark plugs are one of the most common causes of P0304. Take a look at the electrodes and see if they are in good shape. Most vehicles now come with iridium plugs that need changed very infrequently. That being said, the plugs are a great place to start. Here’s a great video on how to see if a spark plug is bad.
• Spark Plug Wires– On most modern engines, the plug wires are not nearly as long as they once were, but they can still go bad. Here’s how to tell if your plug wires are bad (video).
• Coil Packs– Coil packs rarely go bad, but when they do, they can certainly cause P0304 in your Ford Expedition. Replacing a set can be very expensive. Here’s how to test them.
• Bad Fuel Injector– If you have a fuel injector that has gone bad, it won’t be able to properly atomize the fuel and you’ll get the P0304. Here’s a good video on how to diagnose an injector, it can be a little tricky. This is definitely not the place to start.
• Vacuum leak– If your Expedition has a vacuum leak, it can be very difficult for it to get the right air/fuel mixture. This will cause the cylinders to misfire and it’ll throw the P0304 if the leak is around that specific cylinder on the intake manifold. It’s easy (and kind of fun) to chase one down. Popular Mechanics: How to find a vacuum leak.
• Cam or Crank Sensors– This one is very unlikely, but it does happen. If the ECU is not getting the right signal from these sensors, the vehicles timing is not going to sync up and it’ll misfire.
• Low Compression– If you have a leaking head gasket, bent valve, cracked head, etc.. that would cause compression to not be as high as it should, you’re going to get P0304. You should also feel the vehicle is down on power as well.

 

[Dadunn536]

thanks @Petesexpy
Upon rereading, my inquiry, I realize it sounded like I've been driving around with the engine running rough. I parked it as soon as I got it home. I know it's hard on the cats, so I didn't drive it again until after installing new Motorcraft COP, but plug and still had the misfire. Then I just drove far enough to get the CEL to illuminate. That's when I got the aforementioned codes.

It is so hard to get to #4 that checking the wires to the COP is going to be next to impossible. Since it's a bit easier to get to, I was thinking about moving the fuel injector to another cylinder and see of the miss follows it there. If it stays at #4, then I'll move the COP and try again. I know new parts can be bad, but it seems the new plug is the least likely thing to be bad, so I'll save that for last.

I had a bad cat on another car and that manifested in random misfires from multiple cylinders. If the bank 1 cat is plugged, shouldn't I get misfires from the other cylinders (1-3) on that side? Further, the miss is constant regardless of engine RPM. I don't think it's firing at all.

 

[Petesexpy]

so far, the only misfires I ever dealt with were due to COPs.
Sorry can't help you any more than that.

 

[Yupster Dog]

Check to make sure the heater hoses are not leaking down on #4.

What, if anything can I discern from this?

The plastic T for the heater hoses are famous for leaking and causing problems with cylinders below. So looking over heater hoses is always my first stop when it's cylinder 3 and/or 4.

 

[Dadunn536]

Thanks @Yupster Dog
I've been working around those two hoses in order to get to #4, so I've plenty opportunity to discover problems with them. No evidence of leaks in either one for now. They look pretty old though, perhaps original. May end up changing them out as well.
Haven't had time to work on it any more since the weekend, but hope to get back to hit later in the week.

 

[Stephen Dunster]

I once had a new plug go bad from dropping it down into the head when installing it on #8. Found the cracked resistor eventually after I pulled most of my hair out.

 

[Bobmc]

2010 EB, 175k miles. I've dealt with mis-fire codes in the last few weeks. First was #5. Swapped coils, no change. Started to replace the plug and couldn't break it loose and didn't want to break it. (I had a shop change them all @150k). Put the COP back to run it back to the shop and the mis-fire was gone. What changed? I had blown out the plug well w/compressed air and had gotten a surprising amount of dust, sand and dirt. I also noticed some of that dust was up inside the boot. About a week later #3, same thing. Blew the crud out and it was all better. I took the hint and did all of them, putting fresh dielectric grease on the inside of boots. All of them had a fair amount of crud blown back out. Runs great now, hopefully for a good long while.

Next time I'm at the shop I going to ask them about their plug replacement procedure. They must not have cleaned out the plug wells for that much stuff to be in there.

 

[Old Guy]

03, 5.4. I changed 5 COPs about 3 yerars ago. (Thats all the store had in stock, and I needed the car to get to work). A month ago, had another misfire, so I replaced the other three. I found dead leaf fragments as well as sand and dirt. This may have been the cause, however, the new coils solved the problem. I opened the other 5 an dthey had a lot of stuff in them. Cleaned them all and refreshed the dialetric grease and running right now.
When we changed the 5 coils, all the plugs were also changed as it was a 100K maintenance iotem. We blew them out with an air hose before removing the plugs, and after the plugs were installed.I guess the seal at the coil top isn't...

 

[TheWuster]

What cop did you go for? I've had vehicles with two of these motors now through many many miles and the cop has been the issue in 90% off all my misfires. The brand makes a difference. I went with Accel for a while because they were cheaper. I could only get 10-20k out of them before they went bad and had bought at least one bad out of the box. I'm thinking two. I finally wised up as I replaced the last oem Motorcraft after 125,000 miles. Nothing but Motorcraft from here out and I tell you the best of that... One one of my trips to the salvage yard a few years ago I picked up three from low mileage vehicles for $14 a piece. I ended up using two of them for a huge savings before finally putting the Grand Marquis to rest. Soon as I got the Expedition I did the same. I always carry the extras and tools to make a roadside change.