I have a 1999 E-150 with the Titian 5.4 L engine. it is really running rough. Push on gas and hardly no power then it takes off but terrible running. Also when it rains it gets even worst. Someone told me to replace plugs, coil pack and coil. never took one of these a part not going to but there is a really good mechanic down the road here and I was told he is really good with these. But what all would you replace. I would like to replace all the igintion parts so all this would stop. Also going to replace MAP sensor also Just can't stand for it to run this way when you used to press on gas it ran great now press on gas won't hardly have the power to climb a small hill Started this morning ran great for about 5 minutes then press on gas and seems like no power like it is only running on 6 cylnders

 

Not knowing the vehicle's maintenance history, Did anyone try changing the fuel filter?
Why not get to someone who can run the correct tests and replace the defective part(s) instead of throwing money at it and replacing a lot of unnecessary parts?

 

fuel filter replaced

 

Sounds like the EGR system may be working overtime. That might be a good place to start checking.
Also there is a good possibility there may be a problem with either a coil pack / coil on plug system, depending which system is on the engine. Up to date scan tool and test equipment would make correcting the problem much simpler. Let us know how you make out.

 

Disconnected battery yesterday to reset computer. Van ran great. then this morning the light came back on and started running rough again. Got codes for it today and it said P0171 AND P0401

 

The codes seem to indicate the EGR valve/sensor isn't working correctly and you're getting xtra exhaust gas creating a lean condition.