Try this, old tech bulletin, do you have the 'new' style timing cover and cam pin/spring:
Camshaft Thrust Control On Chrysler 2.5, 4.0 & 4.2L (Jeep) Engines
AERA membership has reported a mysterious knocking noise on Chrysler 2.5, 4.0 and 4.2L engines used in various Jeep utility vehicles. The noise is loudest at the lower front area of the engine and has, on occasion, been reported in all of the above listed engines. The noise will disappear if the engine is operated at higher than idle speed.
Disassembly of the engine revealed that the camshaft gear was making contact with the timing cover. Recalling the engine's assembly, several machinists remembered encountering a bolt that had an 1/8 hole in it. Most were unsure where to install the bolt.
As of the 1991 production year, Chrysler has updated the engine to a new method of retaining the camshaft in the block. Prior model year engines were equipped with a camshaft thrust plate. This has been superseded by a special bolt, spring, plunger and front cover (see illustration). The plunger assembly maintains constant pressure on the camshaft, preventing it from moving
forward. Camshaft chucking will result if this thrust control assembly is not reinstalled. The pin rests against a small protruding pad in the front cover that is reported to be 1.000 from the gasket mounting surface.
A replacement Pin Package is available from Chrysler under the Part #83502890.