QuestionMy daughter's 97 Cirrus started running rough. I took to Chrysler and they wanted to replace: distributor, plugs, wires, cap, rotor, fuel sys and throttle body service costing close to $1,800. I said "no". I then bought all of the parts and did the work myself, including spark plug tube seals and upper intake gaskets. The car ran PERFECTLY for one or two days. Then it threw a trouble code of 43 again (cylinder 4 missfire).
I then took it to a shop that I usually have luck with and they again replaced the plugs and plug wires. Car ran great again for a day or two.
It idles rough like it has a fouled plug and is again giving a trouble code of 43. (The plugs were, and are clean.)
AnswerHi Bill,
Here is an answer I sent to an owner with a similar code a while back:
"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."
One other thing that I would look at first, Bill, is the egr valve located on the pipe that runs from the front exhaust manifold to the throttle body. I would try levering the valve stem (the rod between the body of the valve and the round vacuum solenoid on the top, inside a flange that connects the two parts; it has a circumferential slot into which you can insert the tip of a screwdriver to use as a lever) back and forth against spring pressure that tries to close the valve. If the valve stem is cruddy and the valve doesn't close all the way then at idle the mixture is too lean and you will get rough idle (missing). While the valve might be dirty inside, I have found that if you take some WD-40 and spray it on the valve stem it will often free up the spring action and solve the problem.
Let me know what you find.
Roland
