Chrysler Repair: 1992 dodge ram b250 van stalls randomly, oil pressure gauge, oil pressure switch

Question
I recently purchased a dodge 1992 B250 van wih a 318 v8 engine. It has about 150k miles on it. There are no codes set when i flick the key, although the  maintenance required  and  brake  lights are always on. The car would randomly stall, sometimes the rpms would drop way down and it would seem as if it were about to stall but it would catch itself and go back to a normal idle. Sometimes it was very hard to start, other times it started right up. Sometimes it stalled when coming to a stop (low rpms) and it tended to happen when shifting from park to drive or reverse a lot. You could drive for 5 minutes and it would stall and hesitate while driving steadily or while slowing down,sometimes start it and shift and it would die. A local mechanic, after we replaced the oil pressure switch and checked a couple other things (TPS, plugs, air filter..) said egr assembly. The old one seemed clogged where the small metal line comes out of the lower part of the egr valve assembly below the stem. It was better than before.. although this time i noticed that the oil pressure would steadily decrease when i put the car in gear. it would stay below the halfway point and the oil pressure gauge would illuminate red. when i lightly tapped the gas the oil pressure would barely climb (still right around halfway) and then the red light would come on again. sometimes the oil pressure in gear will drop all the way to 0 ! but the car doesnt stall when that happens... other times it dips way down slowly and then climbs back up a little bit slowly. im not sure what to try replacing next.. the car still stalled though after i drove it a couple miles, however it started right back up! its a very annoying problem and i would appreciate any help or suggestions anyone has. i would think if it were purely an oil pressure problem that was causing stalling that maybe it would stall whenever the pressure dropped but this isnt the case.. i have no idea. please help me! thanks -bill

Answer
Hi Bill,
I don't happen to have any experience or manuals for the 318 V-8 engine that you have. My first thought too was that your egr valve was sticking ajar which will cause exactly the sort of inability to idle that you describe. But if you have a new egr installed properly that should not be the cause now. But if you still have the old egr I would suspect that its valve stem is sticking in the ajar position instead of closing when you idle or are coasting to a stop. You can sometime lubiricate the valve stem where it enters the valve body to correct that sort of problem. But after that, I would look for leaks in any of the lines that are attached to the intake manifold to make sure you don't have a vacuum leak which will mess up your air/fuel mixture ratio. Be sure too to check the vacuum line to the MAP sensor which I assume the engine uses for mixture control. It could be the MAP sensor is inaccurate but not so badly as to set a fault code. That could only be detected with a diagnostic reader that gave the parameters for all the sensors.
I hope that this helps you with the problem.
Roland