When I use this scanguage on multiple other cars I notice that when I let off the gas pedal and coast to turn, stop, or roll downhill the MPG shows 9999. That says to me the fuel is not being used on the deceleration. In the 10 months I have watched it on the trailblazer it has only done it a half dozen times. Usually after a WOT sprint to 80mph and let off. But never during regular driving like my 02 suburban did. Can anyone tell me if this is normal for an I6 or is there an underlying problem? It only recently showed up the p0128 code and runs cold. But my main issue was long before this p0128. Any ideas? Bone stock 2002 LS 4200. 160k miles. Gets 18.5mpg hwy 15 city.
Scanguage rarley shows 9999 MPG when coasting
- Thread starter brack2
- Start date
AtlWrk
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- Dec 6, 2011
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Check out post #18 in this thread: http://gmtnation.com/f24/engine-braking-8236/
There are 3 parameters: engine speed, vehicle speed and manifold absolute pressure that determine whether or not the fuel is cut off during deceleration. I imagine it would vary some from year to year. There may be other factors the PCM takes into account too like transmission clutch status, AC status, etc.
For the few times I actually looked for this I never saw my fuel shut off completely--even on a steady, straight, mile-long downgrade.
There are 3 parameters: engine speed, vehicle speed and manifold absolute pressure that determine whether or not the fuel is cut off during deceleration. I imagine it would vary some from year to year. There may be other factors the PCM takes into account too like transmission clutch status, AC status, etc.
For the few times I actually looked for this I never saw my fuel shut off completely--even on a steady, straight, mile-long downgrade.
The Scangauge behavior seems normal to me. I've noticed it does the same thing in my truck from time to time if I'm coasting at a pretty good clip for a little while and I'm not losing much speed.