Chrysler Repair: 99 Sebring PO175&175, penetrating lubricant, engine vacuum

Question
Hi Roland,
Just bought a 99 Sebring LXi 2.5l V6.
The car idles roughly. It seems ok though when you rev it.
Check engine light was on and codes where PO172 and PO175 for system adaptive fuel too rich on both banks. Also, engine was hard to start when warm.
I did a quick clean-up of corroded batteries connections, cleared the codes and now situation is worse. The car is still idling roughly but it also stalls when I apply the brakes coming to a stop light for example.
Previous owner told me he already had the plugs, wires and injectors checked and that it should be the distributor.
The thing that is confusing me now is that I don't get any more fault codes from the ECM.
My questions are therefore:
- do you know a quick way to check the distributor potential faults?
- Why do I only get those two fault codes and not any concerning misfiring / ignition codes.
-What could be the potential cause of the "stalling at stop light"

Answer
Hi Pierre,
I would take a look at the egr valve to see if it might be sticking slightly ajar as that will cause the stalling when coming to a stop. The first thing to do is check the mechanical function of the egr valve which is located along a pipe that runs from the left exhaust manifold (on the side of the engine facing the front of the car) to the intake manifold area (where the incoming air in the large rubber tube enters the throttle). That valve is metal and has a round fitting with a vacuum hose attached, mounted on the top of the valve, and the round part is attached to the main body of the valve by a sort of saddle.  Inside the open saddle you will see a metal rod (with a slot) that connects the round top fitting to to the valve body. That rod is a stem on the valve and it is supposed to go in and out in response to the engine vacuum which varies with RPM and throttle opening (gas pedal position). Take a spray can of WD-40 or other penetrating lubricant and spray the stem where it enters the valve body and then use a regular screwdriver blade tip inserted in the slot to lever the valve in and out to try and free up its motion. Also check all the rubber vacuum hoses associated with the valve and a nearby vacuum solenoid valve. If the valve seems to open (against the action of a spring) and close firmly by the spring action when using the screwdriver blade to facilitate the motion, then you should be able to now start the engine. You can, once it is idling, check that the valve stem moves when you rev the engine from idle to 2500 rpm and back to idle.
The other possibilities are a worn out oxygen sensor, of faulty throttle position sensor, engine coolant sensor, or MAP sensor, although those all have codes when they get bad enough to set a code. You might try taking off the air intake hose at the throttle body and cleaning the inside of the throttle body throat, both sides of the throttle plate and the side air passageway needed for idle air intake. Then let me know and I can tell you about how to assess the sensors, even thought they don't show a code. Replacing the oxygen sensor might be a good thing to do now.
I doubt it is the distributor or anything electrical, but rather the items I have listed that impact the mixture control.
Roland