Question about older OBD1 chevys...map sensor or EGR valve?

[yodaman88]

I have a 1995 GMC conversion van with only 73k miles on the 5.7. It gets a hickup at idle and I'm trying to figure it out. The check engine light comes on after a little driving, but when you park it and restart the light is gone. I pulled the code and it's a code 32, which could be MAP sensor or EGR valve. Rather than guess and throw parts I'd like to get it right the first time.

The engine starts up fine and idles smoothly sometimes, and sometimes it revs up and down a little then smooths out. But as it's warmed up, sitting still at a stop sign or redlight it revs up in short bursts, which causes the van to try to lurch forward. Put it in neutral and it's a smoother idle but still has a slight surge to it. Does this sound more like an EGR or MAP sensor problem? It's cold out and working in the cramped engine bay of a van sucks. Trying to minimize the time I spend out there

 

[Blkvoodoo]

EGR on that should be vacuum operated, and if it gets stuck open, is essentially a vacuum leak directly between intake and exhaust, which would make the MAP sensor read all crappy.

pull the dog house and reach the bottom of EGR valve, you can move it by hand (do this when engine is cool) as the bottom should be open, see how freely it moves. should be smooth and easy, you probably have some vacuum hose issues to tend to as well, because its 24 years old and all....