Hey fellas,

I have a 98 Expedition 4X4 with a 5.4. About once a week, just after I start it and get ready to pull out of driveway or from parking lot it will almost die then come to life and after that it is fine. I have no other issues other than that. I have replaced plugs, coil packs, throttle position sensor, temp sensor, and I see no bad/broken vacuum lines. Any ideas?

 

I would try cleaning the MAF sensor and the IAC valve.

 

I have cleaned the MAF but haven't tried the IAC. Humidity may play a factor i'm thinking because it has rained a lot here lately and has almost died 3 times in the last two days.

 

Did you use dielectric grease when you changed the plugs and cops?

 

Negative on the dielectric grease. Do you think that has anything to do with it?

 

Yeah it might. The Modular engine with where the plugs are located is very sensitive to moisture. Could be you already fried a coil or 2 from getting them wet..

 

I am only having this stumble on average about 1 startup a week and then after that everything is fine.

 

Dielectric grease is REQUIRED - it's not optional.