My Expy is running rough.

[HolidayJones]

2003 Expedition XLT 4WD 5.4

Auto parts store read (Both banks lean; misfire on #4; Random misfire)

Has no problem starting.

Runs rough and randomly misses.

Runs rough all the time, but will randomly clear up for a second or 2, while driving, but 98% of the time it UBS rough, and like I said misfires.

Can't seem to locate any kind of vac leak.

Checked fuel pressure and it close to 33 lbs, which is extremely low, and removing the vac line from the fuel pressure regulator, but the pressure never changed.

So far the consensus seems to be that the fuel pump is going bad.

Just want to see if any one has any input.

 

[Big White]

Grab the elbow behind the throttle body and pull it off. I bet that is the issue. Replace if it is degraded. If rubber comes off on your hand, making your hand black, it's trashed.

 

[FordandPolaris]

Have you replaced the COP and plug on cylinder 4? Personally that is where I would start, since you have a solid code for that. If it is still missing randomly then I would go ahead and do the pump. More than likely you have two separate problems.

 

[HolidayJones]

I have all new plugs and coils

 

[FordandPolaris]

Well then next step would be the pump I think. I would do the fuel filter as well. Have you checked the power at the pump? It is a good idea to make sure the problem is the pump itself, and not a problem in the harness.

 

[HolidayJones]

I just changed the fuel filter, didn't change anything. But I will check out the harness

 

[FordandPolaris]

Just check what you get for power at the pump. The only reason I think it could be power related is that you say it runs ok some of the time. Plus as long as you have a multimeter (not sure if you do or not) it is a free and easy test.

 

[apnt22]

thers an elbow hose behind the intake check if its dry rotted mine did the same thin problem solved

 

[Msport]

Also, check the elbow above the PCV valve. Its hard to see if it has a small hole, you have to remove it. I also have a 2003 5.4 and had to change it.