97 dodge ram 5.9 stalls after cold start.
Amateur
Joined: Jun 2010
Posts: 32
Likes: 0
From: Vancouver
If it's happening right around the time the engine is just reaching normal operating temperature (and so the PCM is just switched to closed loop mode), it's probably your pre-cat 02 sensor.
A little background: The 02 sensor has to be at something like 600*F to provide accurate readings, and if it's yet too cool it will indicate that your engine is running rich. The PCM assumes that if the engine is at normal operating temperature the 02 sensor must be, too, but an old sensor near (essentially just past) its service life won't be quite hot enough quite soon enough for this assumption to hold up. So in the period immediately after going closed-loop the PCM behaves as though the sensor signal is correct and believes that the engine is running rich so it responds by dithering the injectors to compensate.
Revving the engine for a while during this failure mode warms the sensor and the problem goes away for now. But it will get more frequent and continue for longer as time goes on.
Other things can cause the symptom you describe, but if I were a gambling man I'd put my money on the 02 sensor.
A little background: The 02 sensor has to be at something like 600*F to provide accurate readings, and if it's yet too cool it will indicate that your engine is running rich. The PCM assumes that if the engine is at normal operating temperature the 02 sensor must be, too, but an old sensor near (essentially just past) its service life won't be quite hot enough quite soon enough for this assumption to hold up. So in the period immediately after going closed-loop the PCM behaves as though the sensor signal is correct and believes that the engine is running rich so it responds by dithering the injectors to compensate.
Revving the engine for a while during this failure mode warms the sensor and the problem goes away for now. But it will get more frequent and continue for longer as time goes on.
Other things can cause the symptom you describe, but if I were a gambling man I'd put my money on the 02 sensor.
Sorry it took so long but you were right!!! fixed that problem thanks again!!!
Grand Champion
Joined: Apr 2010
Posts: 5,011
Likes: 6
From: Meeker, CO
Yours is one of my favorite stories to retell. The CEL comes on and throws the code when you've got the part in your pocket. What are the odds?!?!
I hope all's well up your way.