Chrysler Repair: we have a 94 chrysler lhs, side exhaust manifold, chrysler lhs

Question
v6 motor, driving down the road, car quits, or stumbles, sometimes it will start and run sometimes not, everytime it quits or stumbles, so to speak, the tach drops to zero, and the cruise light comes on momentarily. goes out then runs ok for awhile, no warning, no consistency to when or what, it will stumble or stall. ran codes and all we get are a 12 code and a cruise relay code, replaced relay, cleared codes, now we get just a 12 code. any ideas??

Answer
Hi John,
I would wonder about a couple of possibilities:
first would be the ignition switch and four fuses that are powered by one section of that switch. When it dies, don't turn the ignition off but instead check to see if fuses 14, 18, 19, 20 all have 12V on both sides of them which would prove that the switch is OK as are those fuses. If so, then it should re-start. If you don't find voltage, then the switch has a bad section.
The other possibility is that the egr valve is sticking ajar. That is located in a small pipe that connects the right side exhaust manifold to the intake manifold at the throttle body. It is mounted in that pipe and it has a round vacuum operated top (vacuum line attached). In between the top and the body of the valve you will see a flange which has an opening where you will see a rod, which is the valve stem. It has a slot that goes around the circumference of the stem. You can use the tip of a screwdriver to move the valve back and forth. It should close to a dead stop by means of an internal spring. If the valve is sticking ajar, that will kill the engine and also make it hard to start. You can try spraying some WD-40 on the stem where it enters the body of the valve, then work the stem back and forth to free up the action.
Those are common causes of simple dieing off of the engine with no codes. Of course the other thing to check when it won't start is whether you have spark or not. If not, then the coil pack would be suspect. Use an insulated handle screwdriver with its tip inserted into a spark plug cap. Then hold the cap and screwdriver together and place the shaft of the screwdriver 1/4" from the cylinder head and have a helper crank the engine. Watch for a spark to jump across the gap while it is cranking. If not, and you have no codes, then I would suspect the coil pack is failing and then reviving.
Roland