Engine wont stay on when started unless you step on the gas,service engine soon " light comes on.Scanned it and you get code po172 system too rich.

Okay, lets start with you checking the fuel preasure regulator, this is a common problem with these the regulator leaks and the vac line connected to it starts sucking gas into the intake, this causing it to run rich and depending on how bad the leak is it will stall engine at idle, remove the vacuum hose from regulator and start engine then see if gas shoots out the vac connection on the regulator, if it does then replace regulator, hope this helps.

Check vacuum line on fuel pressure regulator. A leak in this hose will cause excessive fuel pressure resulting in rich air/fuel mixture. Also check your air filter--make sure it isn't clogged. Another possibility is a leaky injector. You would need to pull off the fuel rail and crank the engine to check the injectors operation. A third possibility is a blocked exhaust system--catalytic converter or muffler. To check for this, race the engine while someone checks the tailpipe for normal exhaust flow. If you have more questions, please let us know.

In your vehicle you have 2 banks which are the o2 sensors so if it says too rich bank one that means your front o2 sensor is bad but if its says too rich on bank 2 then its back o2 sensor that has to be replaced.The o2 sensors are in the front and back of the catalytic converter.Its also called the pre-catalytic o2 sensor and post catalytic o2 sensor.Check both the o2 sensors,but if both o2 sensors checked ok then the catalytic converter is faulty causing this problem of error code p0172. -------------- Keep updated for any further query. Thanks.