Chrysler Repair: Idle Problems, jeep cherokee laredo, jeep cherokee

Question
Hi, I have a 1990 Jeep Cherokee Laredo with a 4.0 liter inline 6 cylinder. It is 4wheel drive and automatic. The truck was running decent although a bit sluggish. This past weekend I decided to change the spark plugs, wires, distributor cap, and rotor button. It started up and ran fine but now a day later the idle speed has dropped to somewhere between 300-400. On my way home from work it almost stalled but I hit the gas just in time. I can't seem to figure out why it is idling so low now and would greatly appreciate any advice. Also I checked for vaccum leaks and couldn't find any.  Thanks in advance for any help you can offer!

Answer
Hi Jordan,
I have to admit a lack of familiarity with that engine or the control system for it. With the feedback systems built-in to most fuel injection engines, a vacuum leak will often be compensated for and the idle will actually rise. The one component that can cause poor/low idling pretty regularly is the egr valve. If that is not closing tightly when the throttle is closed it will slow down and even stall out. The way to check it is to find the valve and then look for the valve stem inside the saddle structure just under the vacuum fitting. The stem has a slot in it and so with a flat blade screwdriver you can move the valve open and it will close back by internal spring action. See if the stem opens and then closes quickly back to closed using the screwdriver tip. If it seems sticky, spray some penentrating oil on the stem where it enters the valve housing. Also start the engine and then alternately rev and idle it and observe how quickly the valve responds to that action.
I don't know of anything that you serviced that would cause such a problem unless you accidentally got the wires misplaced in the distributor cap, or didn't get the correct gap for the spark plugs, or maybe didn't get them torqued to the specified value.
Roland