P0305 Cylinder #5 Misfire

1997 Ford Explorer XLT (4.0L EFI) 218,000 miles.
I replaced the plugs and wires back in March. Last week the check engine light came on and the vehicle was idling rough. I took it to the local autoparts store and I get error code P0305 Cylinder #5 misfire.

To be sure I checked the plugs and they're fine. I tested the wires and they're good and i'm getting a spark from the coil. It could be my imagination but I believe the it's running a little smoother after using some injector cleaner. You can smell a fuel smell as well (smells like a flooded snowmobile). The light will randomly begin flashing and then go back to steady on. I did notice a hole in one of the hoses from the EGR pressure sensor (the hose in the middle between the plug and outer hose) but it's been there for a while. I will be replacing this anyway but it's highly unlikely to be the root of my problem. I wonder what to ask for when I walk into the parts store?

I'm extremely low in funds and i'm looking for some suggestions and guides on what to do next. People have suggested swapping injectors to see if the problem moves. It's a bit of doing but I'm considering trying this weekend.

Reading on some forums I see something about a compression test? I don't know how to do this. Can anyone give suggestions and/or point me to a guide on what to try next? This website suggests:

* Faulty spark plug or wire
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector
* Burned exhaust valve
* Faulty catalytic converter(s)
* Running out of fuel
* Poor compression
* Defective computer

I've tried the first two. Is it possible to test the oxygen sensor? would this be on a single cylinder? Is it possible to test the injector without taking apart half the engine? can I test the exhaust valve? I read the catalytic converter would give off a rotten egg smell if bad, is this true? I have lots of fuel (still loaded with injector cleaner). What's the compression test?

Thank you very much in advance to any help. I'll try to answer any questions anyone may have.

First of all, how did you test the wires? It's nearly impossible to detect a bad wire, even with a resistence test. It wouldn't be an o2 sensor, regardless of what you've read, because an o2 sensor would affect the whole bank, not just one cylinder. When you replaced the wires were they routed so that they didn't rub on anything?

I took the wire from cylinder 5 and swapped it to the adjacent cylinder. The problem didn't move with the wire. The wires were routed the same as the ones that were removed (changed one plug/wire at a time to avoid mixups).

Then you're looking at a cylinder 5 specific problem. So start with the basics. You have spark, so now check for fuel delivery. A compression test wouldn't be a bad idea, but it's a little complicated if you're not familiar with it.

I'm definitely not familiar with it. Before this vehicle the most I had ever done is change my own oil. would you suggest this as the next logical step? or would the fuel injector test be more reasonable?

a good technician would probably be the most logical next step!

I agree but as i've said i'm in a tight spot right now and i'd like to try this myself. That being said I don't think I can do the compression test myself. I can probably test the injector.

Believe me, I would like nothing more than to have a professional look into the problem. As it is now i'm nervous taking the vehicle on the road to interviews and whatnot. I considered taking it to a shop and putting it in for a quote on repair but from my experience i'd be looking at a minimum of $100 just for that and there are still no guarantees on the diagnosis.

What is your opinion on the injector cleaner kits you can buy? If it happens to be a clogged injector I was considering getting one but i'm only beginning to read up on them now.

changing parts that it doesn't require is way more wasted effort and funds then a proper diagnosis! be 100 dollars or 200 dollars! injector cleaning may make it miss less but I've yet to see it repair anything!

I'm not haphazardly swapping parts. I'm attempting to test the various sources that could cause this problem. When funds are limited effort becomes less of a concern. Furthermore, proper diagnosis is questionable even with a professional as you can see all over this forum. Even if the service professional is straight forward and honest this particular problem can easily be misdiagnosed at my expense.

Being new to the area I have yet to find someone to trust. I fully understand your point of view and I wish I could just take it somewhere as i've said. Indeed, this may be what will ultimately happen but not at this time. I have saved a lot of money in the past by fixing problems myself and i'd like to give it a shot this time as well. I'm not a professional and there is a good chance I could fail. Perhaps i've already passed up the source of the problem but i'm still ready to try... even if it is wasted effort.

well if you'd like to eliminate the injector then switch it with one from another cylinder and see if the misfire dtc stays on 5, if it does then it's not an ignition or fuel injector at this point!

Ok, I think i'm ready to leave it to the pros now. I was reading up on the injector swap and though a little intimidating i'd probably give it a shot but not today. Today I went out and played with the wires again. I did notice a wire leaning up against a metal line that I know runs hot and there was slight melting at that spot so I rerouted the wire to avoid future problems there. It had nothing to do with cylinder 5. Other than that I played with the wires some more, tried reseating them again (more out of not knowing what to do so trying something, anything).

There was no difference. I turned off the car. I tried starting it again and it would not start. I tried again and after some hesitation it fired up. The weird thing is it's now running like the explorer of old. The check engine light is still on so I assume I need the tool to clear it (or pull the negative cable but i'd rather do things the right way if possible). I took the car for a spin around the block and it runs like a top. No hesitation, no odors, no stumbling.

The problem now is I am actually farther behind. Most of the things I had ruled out are now possible again. Was it the wires that I played with? or did the fuel injector suddenly clear up? who knows. If the problem resurfaces (and I'm sure it will as soon as I really need to depend on the vehicle) I'll have to start from square one. Well, interviews are picking up so hopefully I'll be able to have someone who really knows what they're doing look at it.

Thank you for all your help. At the very least it was a learning experience.

why wouldn't it be the wires! lots of aftermarket brands are junk no matter how old or new they are!

The wires shouldn't be junk. I paid more for the better wires:

http://www.napaonline.com/MasterPages/N ... +-+Premium

That's not why I had ruled them out though. I switched the wire from cylinder 5 to the next cylinder and the problem did not move with the wire. That's why I ruled it out. Now I'm not so sure. The problem has not yet resurfaced. I drove into the city today and back with no problems (probably 40 miles total).

I've used that same brand before on a 4.6 in an F150 and 2 years later I've still had no problems. Are you sure there's no intake gasket vaccum leak!

I have no idea what it is anymore.
After playing with the wires one day the problem just went away. A couple months later now and it randomly reappeared.

Thankfully i'm in a better spot now. I'm going to try to have it diagnosed tomorrow or the next day.

I spoke with a couple mechanics today and they were suggesting the wire again so I tried a new wire - no go.

So it shouldn't be the plugs or wires. The mechanics I spoke with don't think it's the coil pack because the problem went away for a while (of course this is all preliminary conjecture). I should know more in a couple days.