QuestionQUESTION: Hello. My name is glen and my 1994 chrysler concorde 3.5 V6 has a problem of running well when cold and surging and sputtering and then shutting down after 30 mins. She will start back up running rough (like its on two cylinders). It pulls no codes i've replaced the coil pack module, crank shaft sensor, coolant temputure sensor, fuel filter. NO CHANGE. The wire and plugs are good. I've done a diagnostics with a scanner while vehicle was running everything was in spec. which leads me to the computer. I kno that if its haveing symtoms like that and no code is present and everything is in spec before problem occurs then the computer must be bad. am I on the right track. I kno these cars are notorious for computer issues. If you can help me thank you very much.
ANSWER: Hi Glen,
Have you tried the ignition key to readout the fault codes via the check engine light? If not: turn the key "on-off-on-off-on and leave on" doing that in 5 seconds or less elapsed time. The check engine light remains "on" but then begins to flash, pause, flash, etc. Count the number of flashes before each pause. Then repeat for accuracy. Then group the counts in pairs in the order of appearance. The last such 2-digit number so-formed will be 55 for that is the code of "end of readout". Write back and tell me what codes you got, including whether you got a 55. There are some codes for failed computer so let us see if one of those comes out.
I would also check the egr valve to be sure that it is not sticking ajar. It is located on the right side of the engine near the rear, below the throttle body. Check to make sure that its stem moves freely and that is closes tightly with the help of spring action. The stem has a slot into which the tip of a screwdriver can be placed to test the valve's back and forth action. Make sure that the spring-action full closes the valve to a dead stop.
Other than those two possibilities I can't give you any further suggestions.
Please let me know what you find.
Roland
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QUESTION: Hello, I tried to check the flashes and I got 12, 55 which to my understanding mean nothing to what my problem is. The egr valve spring moves properly and is not stuck open. Which make me think the computer is bad but no codes were present. Thank you so much for your help please let me know if you come up with anything else
AnswerHi Glen,
The timing of the shut down makes me wonder about perhaps the charge air temp sensor not changing its resistance as the manifold warms up, which it should show a decrease just like the coolant temp sensor. So check on that to see if it drops its resistance from cold to hot. In the absence of one of the pcm failure codes I would be reluctant to spend the money for a new one. It could be that one of the sensors is off-value but not enough to set a code. Also chect the wires from the two sensors to the pcm. The coolant signal goes to pin 2 and the charge air goes to pin 21. Their common reference wire (black/light blue) goes to pin 4. It sounds to me like a mixture issue related to being too rich for a warmed up situation. Does the pulse width of the injectors decrease at idle when hot as compared to when cold?
Roland
