I have an 03 Expedition with a 4.6 with 59K miles. My wife ran it low on fuel [maybe out of gas] and ever since the truck will not idle well at all.

I have had the fuel filter changed and the injectors cleaned by Jiffy Lube. It still idles like crap.........dies sometimes when idling.

It runs fine when the car is moving or barely if you barely touch the gas. Isnt there an idle bypass valve or something? Maybe its clogged.


OBD2 Codes:
p0174
p0171
p1151
p1131

All state lean running on bank1 or bank2.

 

It might be possible, that if she ran it real low on gas, that the fuel pump might have sucked some dirt off the bottom of the tank, and plugged up the strainer. Id suggest checking the fuel pressure, and see if your getting 30-50 psi. Cheap and easy place to start.

 

I checked the fuel injection PSI at idle. It is 52psi at idle. Cleaned the idle bypass valve. Tried to adjust the idle screw [wo success]. Still idles with a huge lope. Like it has a big cam in it.

 

Have you tried the battery disconnect trick? If not, remove the negative cable for about 10 minutes then reconnect it. After 10-20 miles of driving the computer will have relearned how to regulate the engine controls, including idle. Running out of fuel could've thrown a monkey wrench into the currently stored learned programming.

 

Would that do the same thing as clearing the codes? I reset the codes on it twice now, using a code reading tool. I have not removed the battery cables.

 

No, clearing the codes does not erase the learned programming. You have to remove power for at least 10 minutes.

 

This is good to know. I will try it this afternoon!

 

Just so you know, for the first 10-20 miles expect the engine to run a bit rough.

Until the computer relearns how to control the engine, it will run on preprogrammed parameters.

 

I found the problem! I had a hole in the tube that connects the PCV valve tot he back of the intake! Replaced the boot that had a hole....5 dollar fix!

 

I'm glad you could fix your problem, I may somewhat have the same issue since I'm experiencing a missing at idle, kind of rough at times, my question to you is, how do you fit you hand in the back of the manifold to feel that hose? I don't know about the 4.6 but as far as the 5.4 goes there is no way I get fit my hand in there, or I'm I doing something wrong? some of the guys say it may be the coils, but I guess that a cracked PCV hose like in your case would case a bad idle too.. so I'll just keep checking.

 

On the 4.6: get something to stand on and place it on the passenger side of the vehicle. The PCV valve is on the passenger side [right side] valve cover. Follow the tube from the PCV valve up to the back of the throttle body. See if you can place your finger on the back of the tube where it connects to the throttle body [90 degree bend]. On the back of the tube were it bends 90 degrees you will find a hole [if this is your problem]. With the truck running, if you put your finger over the hole it will start to idle correctly immediatley, because this is a huge vacuum leak! A give away, that the PCV leak is your problem, is the codes that the computer spits out. If you are getting the same codes as mine, that state the engine is running lean on both banks and you have a rough idle then this leaky PCV tube is the problem. The PCV tube comes apart into 3 pieces and the part that has the hole in it [rubber boot with a 90 degree bend] can be replaced at Autozone for 5 bucks! Go to the Help! section and match it up.

It throws the lean codes because the hole is so big that it pulling in quite a bit of extra air that the Mass Air Flow sensor is not sensing. The Mass Air Flow sensor tells the computer to dispense a certain amount of fuel for the air that it senses going into the engine. This is not enough fuel for it to idle properly or cool the piston tops due to the extra air coming in from the leak. Thus you get that both banks are running lean [lean = too much air not enough fuel].

 

On top of all that I forgot this part. If you are listening for a vacuum leak [while the engine is running] you can actually hear it, but it is so far in the back it took me a while to find it.