I have a 1990 Silverado V8 5.7 2WD. I just bought it a few weeks ago.

The problem:
I can start it with no problems and it seems to idle just fine, really smooth and has never died on me while idling. However, when driving through town I wants to die on me constantly. Highway speeds are fine, doesn't have trouble getting up to speed and keeping it, but when I slow down at a stop light it starts to get rough. And when driving under 30-40mph it will die, or start to die, if I take my foot off the gas.

What's been replaced in the last few months:
Fuel pump
Fuel filter
Oil sending unit
PCV

Any ideas? I looked for any loose or exposed wires that might be grounding but couldn't find any. Then again, I'm not a mechanic by any means so I don't know exactly where to look. Also, if the alternator is bad how would I find out, or test it?

Thanks so much!

 

Figured out the EGR valve is what seems to be the problem. So far so good, we'll see if that fixes it.

 

i'd do the idle air speed controller at the same time