As said above, clean the TB and IAC, also (this may have been a unique case), when I changed out my dpfe the idle got smoother despite having no codes. There are many other things you can do as well such as check for vac leaks, new plugs/wires, etc.
But if you try everything and still want to increase the idle, and have the 4cyl zetek, here's how you do it.
There IS indeed an idle adjustment screw positioned vertically just to the passenger side of the TB, sort of hidden under the allen-headed screw that attaches the black housing bracket for the throttle and cruise control cables, to the side of the TB. That housing bracket is where the cables go from covered to bare. Remove that allen headed screw (its actually a star head but an allen wrench works fine), then remove the idle adjustment screw. You have to remove it and replace it with a screw from the hardware store because even though its there, its head is flat and has no slots for a screwdriver of any type. To remove it get one of
these, then once its out replace it with a 10-24 x 1 1/4 flathead screw, but first grind the edges of the head so its the same diameter all the way down, otherwise the head will not be able to get past that plack metal part of the bracket that had the allen-headed screw in it. This screw is now your idle adjustment, and causes your throttle plate to behave exactly as it would if you were to just slightly press the gas pedal while at idle.
I made one of these for my '95 zetek but have not used it much, since replacing the dpfe smoothed out my idle enough on its own.
You will find it hard to find that point at which the idle is only barely increased, as just a small turn of this screw will make it jump, so it takes a little tweaking to get it right.
Someone will point out the dangers/wrongness of doing this - read their input and assess it. Personally I do not find a problem with it.
Sorry I do not have my digital camera with me this weekend beacuse pics would make this job way easier to communicate. Costs of the job are:
- 5/32 drill bit to bore out the original screw: $1
- screw remover - $3 (not the fancy one in the pic, a basic one)
- new screw - $0.20
. Low idle is good. Saves gas. 