2.8l S15 pickup, surging when warm at low speeds

[grassulo]

my 1987 GMC S15 pickup is surging when it's warm and I'm doing under 10mph, this is very annoying and a bit dangerous, seeing as I almost bumped into a car in front of me because of a surge, I think my fuel pressure regulator diaphragm may be perforated, it feels like a fuel supply problem. The fuel pump, it's screen and the fuel filter, the CTS and MAP sensors, and the O2 sensor are all new. I think the diaphagm may have a hole or tear in it, and at low speeds more fuel than should be allowed is wheezing past it, however, when cold when its in open loop it dosen't do it at all.

-Garret

[geoffinbc]

Do this test for a day or two..

Pull teh Vacuum hose off the EGR valve on teh manifold and plug it with a nail or bolt.

Drive around see if the condition is corrected.

If it is test the valve for free movement and/or chunks stuck in it... If it is fine then replace the EGR Switch.