thdrill

Hey all, like all of us here I love my 03 Tahoe and the versatility it provides me and my family. I have no intentions on trading it in for a more fuel efficient vehicle that won't serve my family the way my hoe does. However I am trying to get the most out of it I can...So far I have switched out the spark plugs to the lsg brisk HALO version, upgraded to the True Flow SAI, and got a performance tune from wait4meperformance. All of this and I haven't seen much in the way of an increase in efficiency...decent amount in performance though . I know I live in Jersey and they do this whole adding ethanol in the winter months, but I was hoping for a little more from the mods. I usually purchase regular (87 octane) fuel from a non-name brand station and am pretty good on tire inflation and routine maintenance (oil changes and all). I was wondering if anyone had any ideas to help me squeeze a littel more efficiency out of this 5000 lb rolling air brake.

5.3L V8
4x4
44500 bought used in August this year now with 46000 miles
Travel is usually local city (approx 90% city 10% highway)[/align]
1) Would not having a crankshaft relearn done after a tune cause the efficiency to not change?...I don't have any error messages after about 400 miles?
2) Am I correct in my asking about a crankshaft relearn or is it a crank relearn?
3) Am I correct in my understanding that the procedure is meant to help the transmission understand the difference between a regular engine firing and a misfire, or is it something different and the reason I am having problems finding a place to get it done is i am not explaining it right?

ZX1100F1

The proper term for what you are wanting to know is "Crankshaft position (CKP) variation learn".

This is usually only required if a DTC code of P0315 is being triggered or after a PCM or Crankshaft position (CKP) sensor is replaced.

The learn procedure is done to calibrate for tiny build variations in engine components which could trigger the PCM to set a false DTC and illuminate the Service Engine light.

thdrill

So is it something that is required after a PCM tune that requires the replacement of the PCM if there are no errors after 400 miles...or is it something I need to look further into?

ZX1100F1

If you have no DTC's set then you are good to go.

thdrill

Would it be possible that even without any DTC's that without doing a crank relearn it could be responsible for a rough idle?

ZX1100F1

Nope