Engine Mechanical problem
2001 Pontiac Grand Prix 6 cyl Two Wheel Drive Automatic 129000 miles
it takes a sec to start and then idles high when it is cold. When it gets up to temp it wont idle right it will bounce from 700 rpm to 1300 rpm and will die after it dose that about 3 or 4 times. I also noticed that when driving it if I let off the gas peddle fast it will die but if I let off slow it will idle at a stop light?
When I checked the codes out it came back with a PO 172 Bank 1 to rich Could it be the egr valve, Fuel presure Reg?
I asked this yesterday and thsi is what they told me Take the throttle-body off and clean it. Check the iac--tps--cts. I wouldn't replace anything, unless I was pointed in that direction.
IAC idle air control, TPS throttle position sensor, CTS coolant temp sensor.
It could be any of them. The IAC and the TPS control the idle speed, but the CTS it what I am leaning toward based on your description. The CTS, located in the thermostat housing, is a thermistor type sensor. As engine temperature increases, sensor resistance decreases. The ECU judges engine temperature by the sensor output voltage and provides optimum fuel enrichment when the engine is cold. If it is not working properly, it can tell the computer it's cold and cause a rich mixture. Thus, your rich mixture (bank 1) and poor idle.
Now keep in mind, there is a coolant temp switch and coolant temp sensor. The sensor, located on or near the thermostat housing, is the one you are after. It is what communicates with the computer.