01 rough idle somtimes stalls

01 Grand Prix 3.8L started with rough idle and now stalls occasionally. I noticed that the torque converter was shifting in and out of lock up on the highway. I dont have a service engine light that comes on and I have been unable to retrieve any fault codes. To date I have replaced the MAF, fuel pressure regulator,throttle position sensor and the o2 sensor next to the firewall. I am not sure what to look at next? :banghead:

Welcome to AF.

It would help to post your mileage. What scanner was used to check for stored DTCs? Best to use one capable of retrieving GM extended codes like P1XXX.

You could have misfire caused by a secondary ignition problem. Were the spark plugs and/or ignition wires replaced? Do you get rough idle when it is out of gear like in park or neutral?

It has 125,000 miles, plugs and wires were replaced this spring. I have an Auto Xray for code retrieval and as far as I can tell when I've used this on other vehicles it will retrieve the Pxxxx codes along with any temp codes. The car will stall in park while I get out to open the garage door, it also has stalled when going down hills and my foot is not on the accelerator.

Uplug the MAF sensor on the trottle body and run it to see if the problem goes away.