1999 Ford F-150 Idles rough and quits when gas pedal is pressed less?

Got it,this types of problems are noticed on many other car models too.
In this types of problem,the car will run properly,if you hit the gas pedal hard or press it too much.
But if you just depress it slow,the car will quit running in between.

The vacuum lines needs to be inspected,EGR valve needs to be inspected.
Also the coil pack and spark plugs has to be checked.
In most of such cases the problem is caused by a bad spark plug and or spark plug boot and usually replacing all eight plugs and boots will resolve this issue. When replacing the spark plugs you are best served to do so with the OE Factory Ford plugs and also be sure to add a small dab of dielectric grease to each boot to insure there is no spark leakage.Also its advisable to get the fuel injector professionally cleaned if your ford is run more then 100000 miles on it.

This details will help.

Thanks.

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