QuestionHi i have a 1996 Chrysler sebring lx coupe 2.5L. My check engine light is on and autozone said that it was multiple cylinder misfire. I replaced spark plugs and wires a couple months ago. I just don't want to pay for a bunch of stuff until i find the problem because i know it can be quite a few things such as cracked distributor cap, fuel injectors, not proper gas/air exchange. I'm just not sure.
AnswerHi 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 including rotor and distributor cap
fuel delivery
engine vacuum, intake manifold vacuum leak
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.
Another idea would be to get a recommendation for a shop (maybe even a dealer?) who had a tune-up/driveability fault mechanic who because of experience would be able to do the tests quickly and intelligently identify exactly what is wrong at minimal time investment. You could try that and set a limit as to how much labor you were willing to invest in then you might get the repair done at an acceptable charge.
Roland
