Chrysler Repair: 1997 Chrysler LHS Engine Misfires, 1997 chrysler lhs, chrysler lhs

Question
1997 Chrysler LHS 3.5 V6

I was driving today and all of the sudden, the check engine light came on. I hooked the handheld computer up to it, and two codes came up. P030 Random multiple misfires, and P0303 Cylinder 3 misfire detected. The handheld computer gave me the same message two months ago, so I changed the spark plugs. Everything seemed to be fine with car, until today when the check engine light came on. The car usually starts w/o a problem. Sometimes I have to turn it over a little longer to get it started. The car idles fine when it is driven at a constant speed, but when I come to a stop light, the car shakes when it idles. I have read a few complaints about this specific problem.  Before I start pouring money into buying a new fuel filter, plug wires, fuel injectors etc. I wanted to ask you what you thought about this problem. Any advice you could give would be greatly appreciated!
Thanks
Josh

Answer
Hi Josh,
The codes are based upon the detection of minor missing which causes subtle differences in the rpm as each cylinder fires to produce its rotational input (crankshaft speed sensor is the detector involved). The Chrysler troubleshooting manual lists the possible causes as:
secondary ignition wires, puel pump or fuel filter, injector harness connectors, ignition coil circuit, spark plugs, mechanical engine problem, contaminated fuel, water in fuel, PCM grounds, Injectors, Restricted exhaust, intake restriction, PCM, evap system, EGR system, Air gap at high rpm's, damaged sensor trigger wheel. That is quite a list!
The approach suggested is to check all electrical connectors and wiring, then do the tests in the following order:
secondary ignition
fuel delivery
engine vacuum
PCM power and ground connections
engine mechanical
The first one uses an engine analyzer scope to look at the high voltage pattern, then spray water on the cables to see if it changes. The possible repairs: individual spark plugs, coil or cable replacement
The second one involves pressure measurement and from there a variety of possible solutions
The third involves reading the intake manifold vacuum to see if it is steady at between 13 and 22 inches of HG. and if not the suspects depend upon the pattern shown by the gauge.
The PCM involves checking various wires at the PCM plugs
The last involves engine compression testing and a variety of other mechanical checks.
So I guess that beginning with the ignition wires makes sense unless you have a scope and the experience/knowledge at interpreting the patterns. You might try looking at the wires in the dark with the engine idling, then also spray some water mist on them to see in either case if you see arcing which would be a sign that the wires' insulation is breaking down. Then measure the coil resistances. If it passes that, then focus on the fuel filter and pump.
The code pointing to cyl #3 means the general problem is affecting that cylinder more than the others, but the approach to it is identical to that for the general misfiring problem, perhaps with a focus on #3. But the 0300 code is probably the controlling factor (involving multiple cylinder misfires rather than just one).
I can't give you any personal experience with this situation, unfortunately.
I'd be interested in learning what you find to have been the solution.
Roland