Chrysler Repair: #4 Misfire, Eng has heartbeat: 3.0L V-6, chrysler voyager, distributor shaft

Question
My check eng light comes on quite often, and the code always ready #4 cyl misfire.  My engine also has a constant 'heartbeat', so that while it idles, every 1-2 seconds, its stutters a bit.  I have replaced the plugs twice and the wires once.  What could be causing this is on a 2000 Chrysler Voyager, 3.0 V6?  Thank you for any insight.

Answer
Hi Art,
Because it is focussed on a single cylinder it could be one of three things: a bad distributor cap, low compression on the #4 cylinder, or malfunctioning injector on that cylinder. The compression should vary no more than 25% between the cylinders with the initial spec of 178 psi measured with all plugs removed at 250 rpm. Check the distributor cap for internal cracks but be aware that the internal contact for the #4 plug wire is actually the one facing the front of the engine due to internal rearrangements in the cap. Check the rotor as well and the distributor shaft for excessive side play. If all that checks out then attention to the injector for that cylinder is warranted.
Roland