Too cool?

[j-ten-ner]

 

My previous '07 Sierra and my '13 Silverado both show in the DIC under "Instant Fuel Economy" that the engine is in V8 mode and the fuel consumption is "0".

When you watch the DIC closely while coasting downhill it'll show the V4 mode and the consumption around 2-3l/100km.

If the decline is steep enough the truck will go faster. At a certain rpm (I guess it is set by default) you can feel the engine starts "braking" a little more.

At the same time the engine goes back to the V8 mode and the consumption goes to 0l/100km.

When the truck slows down again and the engine goes under a certain rpm the fuel supply kicks back in again.

 

Decel fuel cut off is nothing new and I'd be really surprised if GM hasn't heard from it yet.

 

Maybe one of the specialists here can give some input.

 

Thanks.

 

so long

j-ten-ner

 

EDIT

 

I have to correct myself:

The engine goes back into the V8 mode because of I shifted to "M" and chose the needed gear.

But the result is the same.

The fuel consumption goes to "0". And the engine cools down below the average temperature.

 

Sorry about the confusion.

 

so long

j-ten-ner

[esox07]

I think it is as simple as a system that is designed to cool a truck burning fuel at a certain rate. under normal conditions, speed and fuel consumption (burning) vary in unison. The truck burns more gas when going faster which creates more heat which is dissapated by more air flowing over the cooling system. But when going downhill you are burning little fuel which is creating less heat while still going fast which could conceivably, overcool the motor. The converse happens on inclines. You are burning more fuel, creating more heat, while going slower. This leads to possible overheating. The thermostat is designed to control these extreme conditions, but under certain circumstances, it is unable to do so.

[white1500]

Perfect! Are you an engineer or something along those lines?

[txab]

No but he slept at a Holiday Inn Express last night.