Alright my dads 97 has recently developed this rough idle issue. Randomly when its at a stop it'll start to idle really rough for a few seconds then it stops. I figured spark pluggs but its still doing it with even with the new ones. Any ideas?

 

A common problem with rough idle has to do with a dirty IAC (idle air control) valve. I had the same problem. It sits on top of the back part of the throttle body & is held down with two 8mm bolts. There is a better description in these forums somewhere, but I did a quick search and couldn't find it.
Anyway, disconnect the negative battery terminal, disconnect the electrical plug going into the back of the IAC and remove the IAC. Then clean it real well with throttle body cleaner. Use a q-tip or rag and try to get all the gunk off around the spring & plunger inside. While you've got the iac off spray some throttle body cleaner down the two ports going into the intake. While you've got the throttle body cleaner you might as well take off the plastic air intake from the front of the throttle body and clean that out as well. Worked great for me. Some people that have tried this end up replacing the iac, as they do go bad.
Be sure to use dielectric grease around the inside of the plug boots when you change the spark plugs.
Good luck.

 

Cool thanks for the tip, hopefully it does the trick.

 

JT

If that doesn't fix it, look at the vacuum hoses. I had the same problem with my 97 5.4L. Turns out the vacuum lines (over by the battery) were cracked (plastic lines), and causing the occasional rough idle. I would have never found it, but was on that side, and inadvertantly touched to hoses and noticed a hiss noise.

Hope this helps

 

I also found this in another thread, posted by Bluegrass:
"Here is the general cold start and run stratigy as a reference for everyone.
When you turn the ignition to run, on the way to starting, the PCM sees and sets the values in tables, of the cold ECT and IAT.
This sets the level for extra fuel richness and IAC opening for enough air for a cold start and high idle on a cold engine as worked out by test and setup in software.
The PCM begins a timer function after the engine starts, to bring down the idle speed vs time and heating over several minutes if the oxygen sensors don't heat fast enough to take over fuel control by going closed loop
operation. This timer function is short most of the time except in very cold temperatures.
If there is a problem with the smooth control of the IAC the idle speed won't follow the stratigy.
If the ECT or IAT has a fault, this will also contribute to poor idle, stalling, poor fuel economy etc.
Plugs, wires or any item affecting the idle will be a factor and may not set a code if marginal or not lasting long enough.
An EGR valve stuck open or allowed to open by the EVR control will really cause a bad and rough idle. For example if the EVR gets water inside and freezes partially open or the filter is clogged, it will let vacuum pass to the EGR causing it to open and be the cause of major poor idle. The EVR is a 3 port device that has to let air back into the EGR for it to release once it has operated.
Once there is enough engine bay heat, the effects of frozen water quite likely disappear.
All Ford electronic control follows the same general cold engine stratigy from 1985. This kind of operation allows a driver to almost imediately do cold drive away without engine stall on a fuel injection engine when all function are working as designed."