Jake Pride

Quick reason for emergency status: this is my only vehicle , if I can't fix it asap it will seriously prevent me from being able to be with my son.

So I have a 99 lumina with the 3.1l v6. Basically, when it is cold it runs great but normally when it gets to operating temp what happens is that it will violently misfire, Buck, and stall. What I have noticed is that when this happens, if I unplug the ignition control module wait about 30 seconds and plug it back in, it will run fine again for another 30 minutes or longer. So this is telling me that when I do that, something is being reset I'm guessing. I've replaced numerous parts with no results and I'm desperate now because I'm in a rental and only have 4 days left on the rental. Please help! Any ideas or suggestions or if you've experienced this and fixed it please let me know.

So far I have replaced:
Cat
Both o2 sensors
Maf sensor
Tps
Plugs +wires
All 3 coils
Ignition control module
Cleaned egr system
Idle control valve

tech2

which 02 sensors did you replace? some w bodies only use 2 others 4. did you replace the pre cat 02 sensors? the post cat 02 are not used for fuel metering. the 02 sensor data is ignored until the system goes into closed loop operation.

-what dtc are setting?
-what are the fuel trims at when it enters closed loop operation? provide both banks at idle and 2500rpm
-what is the ect sensor reading?
-you may need to verify no spark when it starts misfiring. if spark is present you can rule out the ignition system.


-what is the map reading at key on engine off?

to me, it sounds like it runs fine in open loop and starts misfiring once closed loop operation starts. If that is the case...you will need scan tool data to fine the bad sensor that is skewing the fuel metering.