hesitation/stumble....help

[97yelstang]

ok my car has approx. 100k on it and i just replaced the iac and it ran fine
now whenever i'm at a cruise or leave my foot at the same spot on the throttle for a long period of time, the car will start to hesitate and stumble but the second i jump on it ..it has instant throttle response and and power is like it should be
but as i said b4 if i'm just cruising and leave my foot in the same spot it will start the buck and hesitate and stumble but then i hammer it and its fine ...until i back off the thottle and just cruise again.......*now occasionally it will hesitate when i rip on it, but that is only once in a while
today i'm gonna change the plugs but i know thats not the problem and fuel filter was done , not too long ago
i would appreciate any info thx

 

[Kilgore Trout]

I suggest you SeaFoam and reset the PCM while you are working on it today also.

 

[Mike97gt]

99 percent of the time I find this to be the plugs. get some stock replacement motorcrafts..

 

[BMan5150]

DPFE sensor? I believe this is the sensor that regulates EGR - since you're having a problem at partial steady throttle but it's fine at WOT and you've already replaced the EGR valve, this might be your prob.

Check/change the plugs, then give this a try.

 

[03ghoststang]

99 percent of the time I find this to be the plugs. get some stock replacement motorcrafts..

i agree with mike, but when was the last time you changed the plugs

 

[squares98]

I suggest you SeaFoam and reset the PCM while you are working on it today also.

It worked when I had the same problem, but I think my plugs had buildup on them from all the horrid tuning early on.