I have yet to find a vacuum leak. The PCV is rattling when I shake it as it should. After driving it a while I am noticing the stutter between 1500 & 1900 rpms under light load, give it gas and it kicks down and smooths out. The truck seems to have enough power. I spun the tires pulling out a while ago. It idles smooth in park, but in gear it stutters and runs rough. I am trying to get the new EGR Valve on but I have not been successful in getting the EGR loose from the tube to the exhaust. The nut is so corroded I can't get a good grip on it to break it loose. I am using pb blaster but no luck yet.

 

EGR valve is welded stuck. I heated it to orange hot and could not get the nut to let loose. The only alternative is to take it off at the exhaust and take it out and work on it on the workbench. That does not look easy either. I will have to climb under and see if I can get a wrench on it from underneath the truck or through the fender well. Inner fender may have to come off too. Truck is idling irradic now. It will run fine and then all of a sudden it starts stumbling for no apparent reason, then it will straighten up and run fine. Nothing seems to be consistant. The other thing I noticed is that when you go to fill the tank up it does not want to take gas like the vent is plugged. The hose does not seem to be pinched anywhere that I can see anyway. Could this cause problems? I am thinking about changing out the fuel filter to see if that will make a difference. This is driving me nuts!

 

If you physically touched the MAF with a Q-Tip it is most likely damaged.

Both your O2 sensors are reporting a lean condition. The odds of the left and right O2s both going bad at the same time are pretty slim.

You either have a MAF problem (likely since you touched it), or a vacuum leak somewhere.

 

As far as the q-tip cleaning, I found this youtube video on how to clean the MAF and he used q-tips. The only difference was that I used CRC electronic contact cleaner. I have since found other videos that say do not touch wires. I was very careful not to damage the wires. In another video I found 7 symptoms of a bad MAF.

1) MAF Sensor codes. (I do not have any.)
2) Malfunctioning MAF does not light the CEL (I have a lit CEL with no MAF codes.)
3) Lean or rich code (Yes I have lean codes.)
4) Lack of power (I have good power.)
5.) Black smoke from tail pipe (I do not have black smoke.)
6.) Bad gas mileage (I have not notice a significant loss of gas mileage.15 mpg +/-)
7.) vehicle idles rough or stalls (It does idle rough sometimes, mostly in gear. Has stalled occasionally but not consistantly.) It idles perfectly in park.

I have only 1 possibly 2 out of 7, but they relate to a vacuum leak. I have checked, double checked, and triple checked and can not find a vacuum leak. PCV in not stuck. I do have some oil seepage from valve covers but not a lot. I am leaning more toward an electrical problem with either the battery (which tested o.k. at Advance) or alternator (which was load tested on the vehicle as o.k. also.) The battery light has been staying on sometimes but also not consistantly. I am thinking about taking it out and tested out of the truck.

Another thing that bothers me is the fuel vent pipe being plugged up. It is almost impossible to get gas in the truck without it shooting back at you. I have not found how the tank is vented yet. If anyone has any info please let me know. Sorry for the rant but this is driving me nuts.

 

Have the lower manifold smoke tested or use TB cleaner.

Testing with TB cleaner will take 5 minutes at the most, listen for

slight RPM change. The 4.0s are very prone to manifold leaks.

 

I plan to replace the gaskets next week on the 00 Explorer.

 

That is the only vacuum test that I have not tried yet. I have visually inspected (what I could see anyway) the lower manifold for gaps or cracks but have not found any. I will try using TB cleaner tmorrow if the weather holds up. Thanks guys. It does not look too difficult to change out the gaskets.

 

100 bucks or so.
One day at the most.

This is what I bought, I donʻt know your engine code. Yours should
be similar as far as cost goes.

Fel-Pro MS98006T - Intake Manifold Gasket Set | O'Reilly Auto Parts

also might as well change injector o-rings if you do find
a leaking intake manifold gasket.

Please donʻt use touch the MAF wires in the future!

 

I finally got around to taking the alternator off and having it tested today. It tested bad, I had suspected it for awhile. I bought a brush kit and put it on but that did not help. I will check to see if there is a rebuild kit before I buy a new one. I will report back when I get it on.

I also tested the intake gasket with throttle body cleaner and no change in idle.

 

I put a remanufactured alternator on today and the truck is running better, no missing. The other problem I have is that when the OD is on it will shift down to 1500 rpms and shutter like it is in too low of gear. Give it gas to shift up and all is well again. Does anyone know what might cause this? It will do this around speeds of 35 & 55mph. Turn OD off and it does not do it due to higher rpms. The only codes now are P0171 & P0174. With 121,000 miles I might have to invest in O2 sensors. I found a few vacuum hoses that might need replaced, they don't leak but they are almost dry rotted. Another thing I noticed this evening was when I went to defrost the windshield the air was not blowing out very good on the drivers side. Is this vacuum controlled?