I have a 92 jimmy with a vortec engine 115,ooo miles. It started with a egr light, replaced egr, then the cpi unit as it was leaking, put in new ac plugs and cap and rotor, plug wires, andt temp sensor. It idles perfect until I put it in reverse or drive then it has a slobber idle. give me some ideas.:banghead:

Welcome to AF, post a better description of what is happening for any meaningful help.

it acts like it is missing. when you put it park or neutral it clears up