Need help with idle problems

[akara]

Yesterday my wifes '03 4.0 explorer started acting weird going down the Interstate. Idling rough, acting like it has no power. Wife pulled off at a gas station and wanted me to drive the rest of the way to our destination. Resting it was running really rough, idle jumping like crazy, but no CEL. I got back on the highway and it was acting worse, and the CEL came on, so I changed route to an Auto Zone to get the code pulled. Get off the exit and it has 0 power. wont pull a hill. I pull off into a parking lot and after cooling for about 20 minutes, it runs well enough to get to auto parts store. Pulled codes are as follows

P0174 System too lean (Bank 2)
P0300 Random Misfire Detected
P0316 Misfire Detected on Startup (First 1000 Revolutions)
P0304-0306 Cylinder 4-6 misfire Detected
P2197 O2 Sensor Signal Stuck Lean Bank 2 Sensor 1

Auto Zone recommended fix is PCV valve, a $6 part with an easy replacement. Replace it and reset battery. Seems to be idling and running ok, but its also set for about an hour at this point. Leave idling for a few just to let it warm up, and no hesitation until i start to pull out. Acting the same and now won't go over 2k rpms even in park. As I already suspected, everything online for P0174 seems to point to stuck EGR valve, problem with MAF sensor, intake gasket bad, or busted vacuum line, but everyone else seems to only have the one code. Having reset the battery, the CEL won't come back on and I can't drive it far enough to let it reset and pull new codes to see if the PCV valve even fixed anything. Looking for tips or advice on this vehicle's issues from those who have had these longer than I.

 

[akara]

if it helps, the ac is stuck in the defrost feet position and ive read somewhere that the AC switch is tied to the vacuum system. I'm heavily leaning towards a vacuum leak somewhere, but not sure where to start.

 

[Gmctyphoon]

If it’s a vacuum leak bad enough to make it run like you say, then I’d suspect you would hear the leak. Pop the hood and listen for any whistle sounds while running. Also try listening while your wife shuts the engine off. Might hear the broken vac line while the engine shuts off.

 

[Kotter]

My Explorer was throwing similar codes recently (Random Misfire Detected, Misfire Detected on Startup (First 1000 Revolutions), and Cylinder 4 Misfire Detected). I ended up changing all of the spark plugs which seemed to have fixed the problem, haven't gotten those codes in weeks now.

 

[akara]

Can't hear a vacuum leak so I don't think that's it. I had the same thoughts on the spark plugs, so tried that first to no avail. Getting it towed home Friday so I can look at it a bit easier. Hard to do much when I'm driving 1.5 hours just to get to it and back home. Going to try the MAF sensor first as everyone I talk to says that seems most likely. I'l also pull the belt off and check the pulleys once i get it home to make sure that a bad bearing isn't causing the issue by making the belt slip too bad. I don't believe it is, but its free to check, so why not lol. Thanks for the advice guys.

 

[Gmctyphoon]

Per your code list everything wrong is on the driver side bank. All three cylinders on that side. A maf sensor or anything attached to the belt would affect all cylinders.

I would be looking at things only on the driver side of the engine. I think the egr is. Intake gasket or cracked intake manifold could do it. A vac line on that side could do it but I doubt it would make the engine run that bad.

A cracked manifold or badly leaking intake manifold gasket is pretty easy to diag. Just spray some flammable brake cleaner (yes, parts stores sell non flammable stuff now) around the suspected areas. Obviously while the engine is running. The idle will change if there is a leak.

Other than that stuff it might be an internal issue.