At idle and applying light trottle, the engine feels like its about to stall then recovers. It happens about 2 a second. Once I apply a little more throttle, it goes away.

I've recently changed the plugs, cap, rotor, O2 sensor, air filter, oil. I also have a fuel filter and PCV valve that I'm going to replace. I didn't change the plug wires.

Does anyone have any ideas on where to start? Could it be a faulty sensor?

It's a 1991 Trooper 2.8L V6 Auto

mebbe a vacuum leak somewhere ?

Is it throwing any codes ?

Mebbe check out the EGR circuit too...

I did check ou the vacuum lines. I'm not sure if the line was cracked before I started or after - all i know is i ended up snapping two of the vacuum lines trying to inspect them - they were amazingly brittle. I guess after 15 years, things are bound to fall apart.

After I replaced the vacuum lines, it did seem to get better, but has since returned.

What's a good way to check the EGR circuit? I pushed in the EGR valve, and it didn't take too much pressure to move, so i think that it's working okay. Could there be more to it that's causing the problem?

Thanks!

If they're that brittle, they might be leaking.
Get some starter fluid and start spraying carefully around the engine.
If you have a leak, generally the engine will race when the starter fluid hits it.

You need to check the EGR with the engine running. When you push it the engine should bog down which would indicate the exhaust gas is
getting to the right place. If it hasn't been cleaned in a while I'd recommend you take off the EGR valve and give it, and the port, a good
cleaning with a synthetic carb cleaner. They carbon up after a time and cease to function.

Vac lines can also develop small cracks that leak air in where it shouldn't be. It's a cheap fix just to get the right tubing and replace them all to eliminate that as a problem.

TPS maybe?