QuestionQUESTION: Hi, My daughter has a 2000 dodge neon. One month ago she was driving and lost power. After sitting for a half hour she was able to drive it again. We brought to a shop and they put in a crankshaft sensor. 2 weeks later same problem. Brought to Auto-Zone and ran a scan of the check enginge light. Came up with error codes PO300, 301,302,303,304. Put in new plugs and wires and seemed to run good. Today 2 weeks later she breaks down again after driving for 40 mins. Pulled up same error codes as before. Any ideas??? I was thinking something with the coil as it only happened when it was hot.
ANSWER: Hi Mike,
It certainly could be the spark coil, and you could check the resistance of the primary windings to see if they are about equal and also the resistance between the paired high tension towers to see if you find any discrepencies in the readings that would support the theory that the coil is the problem.
Also, listen to hear the injectors clicking evenly at idle.
You could pull the plugs and see if any of them look excessively wet which would implicate an injector(s); and you could do a compression check if you did that with the engine warmed up
Check the PCV, or even just change it.
Finally, I would check the egr valve to make sure that it isn't sticking slightly ajar. You didn't mention which engine is in the car but try to find the egr and then look in the flange area between the vacuum actuator on the top and the valve body proper. In the flange area you will find the valve stem and it has a slot into which the tip of a screwdriver can be inserted and that allows you to test the valve action. An internal spring tries to close the valve to a dead stop. See if it does so. If not, then spray some WD-40 on the stem where it enters the valve body proper. If that were struck ajar it would cause multiple cylinder misfires too.
Sorry to give you such a long list, but there are unfortunately many reasons for misfire and which can't be detected by the self-diagnostics of the engine.
Please let me know if any of theses bear fruit.
Roland
PS You can get back to me without having to wait for my "availability" by using the "thank/rate" tab below where there is a section for comments.
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QUESTION: Hi Roland, I have the 2.0 engine in the Neon. I have tried to find the EGR but am not able to find it. The auto parts stores dont even list one for this car. Would you know where it is located? I have checked the injectors and they seem to be firing fine with no wetness on the plugs.
ANSWER: Hi Mike,
The egr valve is attached to the rear of the cylinder head at the right corner as you view it from the rear of the engine. You will see a pipe from the exhaust manifold that runs around the rear of the engine and into the valve. You will probably need to remove the air intake hose to see it buried under there. Let me know what you learn about its functioning and whether that helps any with the multiple missing.
The P0300-on 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.
Roland
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QUESTION: Thanks Roland, I will go find it. Also the check engine light went out and it was tested yesterday and there are no codes on it. The car was driven all day yesterday with no problems.
AnswerHi Mike,
That is good to hear that there are now no codes. I sent you more info about other possibilities for the O300 problem if it recurs. The intermittency is the sort of thing that a sticky egr can cause, so I would suggest that you check out the valve stem's motion.
Roland
