98 Expedition running very rough

[cvpi71]

Hi Folks

I just recently acquired a 98 Expedition 5.4 2WD. It had a misfire in Cyl #1 , #5 .It has 195k miles, I did a tune up using Ford spark plugs lugs and replaced all the boots and springs on the coil and replaced 2 bad COP. It runs great when it been sitting for a while or cold and after about 10 minutes of driving it feels like it's stumbling and misfiring running really rough feels like running on 6 or 7 cylinder. No CEL or flashing CEL. Once it's warmed up when you come to a stop and have to step on the gas it feels like you are on the rumble strips, it feels like this every time the gas is depressed. I am running out of ideas. When it's cold it runs flawless, no stumbling or shaking from the engine. Thanx

 

[green03]

possibly the TPS sensor if it only does it on aceleration

 

[GRIP]

after it warms up does it run rough just sitting there or only when you hit the gas?

 

[expeditionman]

Check the IAC. Could be gummed up or bad.

 

[AvroAero]

I'd try the TPS also. Test it with a meter and someone pressing the pedal/you opening the throttle plate. You should get varrying resistances without any drops to 0.

 

[slo-ryd]

Try cleaning the MAF.

Sounds like the problem starts about the time it goes into closed loop.

 

[cvpi71]

well I unplugged the battery, change the fuel filter, added a bottle of octane booster, connect the battery after 30 minutes and everything is fine now, runs smooth and powerful. Jump on the highway and put on about 120 miles. No CEL or stumbles or miss. Thanx everyone for their help.