Hello, when it gets down to about -20 C and I don't plug my truck in when I go to start it it starts fine. Except when it gets down to about 1000 rpms it starts to run like crap and usually will stall. I've had a scanner hooked up to it and what seems to be happening is the O2 sensors areleaning right out to 0.020v and lower. I've check the fuel pressure when cold it's at 48 to 49 psi with the engine running. Has anyone else seen this problem or does anyone know whats wrong with my truck.

 

What year is your truck?
Engine?
How many miles?
How does it run after you restart it?
Is the .2v reading constant or does it go up and down (engine idling)?

 

Sorry, about that. I thought the paticulars would've shown up on the bottom. I filled in the signature box.

It's a '02 Chev Silverado 1500HD 6.0L 4X4.

After restarting it it does the exact same thing Once it gets below 1000 rpms tries to stall out. The oxygen sensors are up and down between 0.000v and 0.020v while it's running like crap. Then after it's running normal after warming up they show normal 0.1 to 0.9.

The truck has 150,000 km. I've done all the scheduled maintainence.

 

OK it sounds as though you need to replace the O2 sensor(s).
They have a heated element built into the sensor that brings the temperature up on the sensor very quickly when the engine is first started, the sensors won't produce voltage until they get over 500F or so.
When you first start the motor the heated element in the sensor brings it up to operating temperature instantly and then the heat of the exhaust keeps it warm, if the heater doesn't work then the sensor won't work properly for a while until the exhaust gases warm the sensor to operating temperature.


Dave

 

Wouldn't the truck just stay in open loop until they do warmup like I'm pretty sure it does. Therefore it would ignore the O2 sensors. I thought the sensors might be reading right cause they show a rich condition while the truck is warming up and then as the truck starts to run like crap I can see the O2 sensors reading almost 0v.

 

I didn't know that that the O2 sensors were giving out proper ranges until full warm.

Check for leaky intake manifold gasket, this is common on the 6.0L engine and 99% of the time will cause what you describe.