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feed back TDCO from -0.18 to -1.94

Maybe they didnt tighten the nuts down and its moving :)

You should get a scanner to see what they set TDCO at and then to the koko procedure and see if it changes.
 
Trying to make it survive MY WIFE'S right foot

-1.8 to -1.94 should not be that much of a change, now -.75 to -1.5+ is night and day difference, once you get above -1.4+; beyond that net results will be vehicle/IP health individuality dependent results, -1.94 may not be the best, to "dial it in" for your truck, IMO one has to play with it to determine what is best for their trucks health.

Would probably restore timing close to when she was showroom clean, and tight engine tolerances... timing chain specifically... I'm sure the 200k has retarded things over the long miles. IP Wear, etc.

Mods don't kill trucks. Mods increase longevity at all ages......

:iagree: The right mods... not a TM set for 25psi:eek: not mine.

With over 230K miles, free-er flowing intake and exhaust, Walbro frb5 Racor pre-LP, heath FSD, TM, and basically stock otherwise AFIK (chip, injectors, etc), how much should I move the adjustment?

Is this the same as an "optic bump"?

Which scanner should I get (on disability pay) = cheap as I can get and still use it to set the good numbers?

I know, I could probably find this stuff after a few hours of searching, but I'd rather ask youse guys, and Missy if she cares to chime in...
 
It is not the same as optic bump. Optic bump will always inject more fuel than the PCM is calling for at all stages except for idle. The PCM uses a different method to control idling which constantly adjusts for cylinder imbalances and other possible fluctuations. Not sure how DB2 (mechanical pump) handles idling with effect to optic bump. I assume there is a idle screw similar to carbs. Changing the timing simply advances the timing curve that the same (proper) amount of fuel is injected earlier.

This is why most report driveablility issues with OPtic bump, and 'trailer hitching' with CC engaged. Even going as far as to be tough to drive on crappy dirt/rocky roads from what I've read. Super sensitive throttle, especially from idle to acceleration. Interesting enough this is similar to what I feel with 10psi compared to 5psi at the IP. HOwever, there are no driveabliity issues, or trailer hitching going on.

I'll leave the scanner Q alone for someone with a 94 to chime in.
 
GMTDScanTech is the best tool out there for these trucks.

Optic Bump involves taking top of DS4 off and moving the OS. For the TDCO you are moving the whole IP. I can accomplish the same effect as optic bump in programming.
 
GMTDScanTech is the best tool out there for these trucks.

Optic Bump involves taking top of DS4 off and moving the OS. For the TDCO you are moving the whole IP. I can accomplish the same effect as optic bump in programming.

Theoretically speaking, can't you alter timing and the advanced effect via programming also?
 
true I can advance it to whatever, whenever, but I dont think that you are actaully advancing anything when you change TDCO (other than base timing that you never reach when driving), but effecting the internal IP pressures so that more fuel is being metered. The timing reference is external from the crank sensor, and moving IP wont alter what it reads.
 
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