I have 1990 Jeep Wrangler 4cyl. 125 thousand miles 25 years old. I encountered the same problem and it took some doing to correct.
The good news is that there are parts available for this year model jeep, and second, it all required very little labor to achieve the "Fix".
First off I had issue with knocking valves when starting specially in very cold weather.
Fix: Drained oil and changed oil and oil filter THIS WAY. 3 1/4 Quart of 5w30 oil, (not 10w40) and one Quart of RIZLONE OIL . (Jeep takes exactly 4 1/4 Quarts of oil including the oil filter.) Knocking stopped instantly when starting in very cold weather. Next oil change in cold weather, always 5w30 oil. (Hot weather 10w40 oil)
Next issue was rough idle .
Fix: I replaced the EGR valve. That took care of most of rough idle and amazing speed power in all gears. However it still idled (less) rough and it was "Hiccuping" at 40 50 and 60 miles per hour. At this point I changed the OXYGEN SENSOR. This ALMOST completely eliminating the rough idle and NO MORE HICCUPS.
Next I changed the spark plugs,spark plug wired rotor and distributor cap.
It runs perfect now. The big expense was the EGR Valve $99 and OXYGEN sensor $55.
I hope this helps.
E mail me. manny