I have a 96 explorer with a 4.0l 4x4. I've been replacing a lot of parts to pass our state inspection and unfortunately, more problems have been creeping in as I fix others. I started with P0401, p0305, p0171 and sometimes p0113 and p0174. I replaced the plugs and wires, the DPFE sensor, cleaned the MAF, replaced the vacuum lines to the DPFE sensor due to some cracking and installed a wire tie on the IAT connection because the clip had broken off and replaced the fuel filter. At the same time I installed new inner tie rods and upper control arm on the passenger side and shackles on the leaf springs. I cleared the codes and took it for a test drive of about a half mile, when I returned and parked in the driveway, the water pump started leaking. I replaced the pump, topped off the coolant and warmed it up with no issues. Took it for a 45 min drive to return the fan clutch tool and a p0171 showed up, but ran fine otherwise. When my girlfriend took it to work, it started misfiring and blowing smoke. It now has codes p0304 p0305 p0306 p0171 and p0174. I know what obd2 says they mean, misfires on 4 5 & 6 and lean on banks 1 & 2. But does anyone know where I can start to fix them?
As far as conditions on it now, when I got to her work to take a look, I didn't see anything obviously disconnected like vacuum lines or plug wires. The alternator seems to a little noisier than I recall from earlier today and there's a small puf-puf-puf (best imitation of a exhaust? leak) coming from the passenger side.
I had her towed home and she's sitting in the driveway, waiting for me to get a clue on where to start.

 

The both banks is showing misfires, did you disturb the intake manifold,

A manifold leak will cause the misfires (lean) and throw the intake leak codes..

Any upstream exhaust leak will trigger O2 to lean and ECM/CPM will flood fuel to compensate...

 

Not that I'm aware of. The only engine bolts I touched were the 3 on the alternator bracket and the 12 on the pump.

 

Check the breather tube from the passenger oil fill to the intake tube between air box and throttle body.

You have created an illegal air leak somewhere... Philip

 

I pulled it off and looked to see if somehow a crack or leak had gotten by me before, but I didn't find anything out of the ordinary with it. That being said, it was raining sideways when I was checking it out, so I'll be more in depth tomorrow.

 

An update on the explorer:
I replaced all the intake gaskets and injector o rings and put it back together. Unfortunately nothing changed. The #5 plug was a wet and the intake to it was oily/wet so I'm thinking either the head or the head gasket is my problem.
Autozone and Advance sell reman's for about $250, so unless I find a totally shot gasket I think i'm just replacing the head.

 

You are getting ahead of your self...

If the intake runner is wet, that is before the head..
Check your PCV....
#5 was wet with what?? Fuel, water??

 

Both actually.
There is also a watery oil mix coating the #5 passage up into the upper intake.

 

Is your exhaust manifold cracked? If you moved your plug wires from the factory routing , you can get a missfire. But your missfire sounds more serious than that. did you get your DPFE hoses reversed?

 

The only exhaust leek I'm aware of is at the joint after the cat.

I tried to follow the original routing of the wires, but it's possible they could be slightly off as the run behind the upper intake.

Nope, the DPFE lines are correct.

A little more info I pieced together today:
After I replaced the intake gaskets I had the radiator uncapped as I topped the water off with the engine running. The exhaust smoke let up and it seemed to be running better. So I did an oil change because a small amount of coolant did drip down when I originally pulled the lower intake and I didn't like the white coating I had seen on the intake. After the OC, I closed up the rad cap and as it warmed and the pressure rose, the smoke got worse and it started missing on #5 again. I shut it off and pulled the plug and it was soaked with water and gas.
When I pulled the upper intake after that, The #5 channel was again coated with white.

 

Sounds like coolant is leaking into your intake. Do a pressure test on your coolant system.

 

Did you remove or replace your thermostat when you were replacing your water pump? If so make sure you didnt install your t-stat backwards or upside down.

 

The only spot in the lower intake that has the coolant is the front section, correct? I don't believe there are any passages through the intake.

How would it get into just the #5 through the intake? I was thinking head/headgasket and after the plug fouls that it was just working its way up backwards.

 

Nope, no thermostat work. Not this time anyway. Did it a while ago and haven't had any issues.

 

Another update:
I pulled the drivers side head and I was right. The block side of the gasket had failed on the water jacket hole at about 11 o'clock above #5. The cylinder was full of coolant when I opened it up.
A bit of running around to get a new gasket and a couple other parts and hopefully the rain will be goon tomorrow and I can get it back together.