QuestionHi, I just finished a complete rebuild on a 2.7 V6 engine for a 2001 Stratus. The engine runs/revs great in park or nutral but when I put it in reverse or drive it idles rough and stalls when I come to a stop. I am getting a generic code PO172 (system too rich, bank 1). I have replaced the auto transmission valve control module and the idle air control motor with no change. Any suggestions?
AnswerHi Steve,
There are many possible causes for that code (rear bank of cylinders oxy sensor too rich) or the 0175 shich applies to the other bank of cylinders.
It may be that one of the injectors on the rear bank is sticking open so pull those 3 plugs and see if any one looks wet. Another possibility is the oxy sensor on the rear bank has failed due to a bad heater coil in it or the sensor itself or its wiring of those 4 wires to the PCM.
You might also have an egr valve that is sticking slightly ajar due to crud that is on it stem. That often manifests itself by stalling when accelerating or coming to a stop and/or hard starting but reasonable running at a steady speed. It is not a well-monitored part so I like to mention that when stalling comes to light.
The other items listed are evap/purge solenoid operation, TPS sensor, MAP sensor, too high fuel pressure, partially plugged catalytic converter, or engine mechanical problem (non-specific).
I wish there were fewer choices to consider, but prioritize them based upon "history" and difficulty to check out each.
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Thanks,
Roland
