I may have screwed the pooch with trying to reset timing help. Car Code OBD2

[schiker]

My truck has a surging at launch when its cold but after it warms up past 170F coolant temp it launches smoother. Since I had replaced the timing gears I thought why not investigate timing and TDCO since it might be 50 starts since then and relearned to start causing this surging.

I am using Car Code OBD2 Laptop as my scanner. Software is confusing am using enhanced data for GM diesel L56 6.5 K98 window. My understanding is
IPT =injection pump timing, IPTD= injection pump timing desired, TDCO=Top dead center offset.

Engine warmed up I start with
IPT = 12.0 (My understanding isn't this suppose to be 3.5)
IPTD = 12.3 (depends on PCM and curve varies with RPM)
TDCO = -0.09 (isn't this suppose to be -0.25 - -0.75)
I say to self I think my injection pump is advanced too far and with cold advanced its a bit hard to control idle on launch warming up.

I tell myself IPT 12.0 - 3.5 = 9 degrees advanced so if 1mm is 2 degrees I need to retard pump ~4mm marking the top of IP at flange then move IP mark towards passenger side about 4mm. It cranks up fine I do KOKO engine stumbles and then settles down but is smokey idles rough and timing isnt correct below 0. I move pump back to drivers side about 2mm advancing it IPT is still below 3.5. When I cranked it up it ran ok while warming up timing advanced once over 170 starts to run rough. But I want to see how it launches I drive it down road and it seems flat till rpm's rise; launches smooth though. I take a break.

Go back out let it idle to warm up and service engine soon light is on. I think timing is retarded too much and causing wierd issues. Kinda freaks me out so I write this post to make sure I am on the correct path.

I have now:
IPT 2.2 ( So I assume I need to advance it a bit like 0.65mm towards drivers side to get to 3.5 timing set point then KOKO procedure)
IPTD 12.6
TDCO 2.46 ( I think this is irrelavant because IPT below 3.5 but not sure what really to expect think it will learn something in acceptable range when IPT is 3.5 or little higher)

@Leroy or anyone else with Time Keeper gear set should I be aiming for a little higher IPT say 3.5 to 8 ?

With KOKO should I do anything or just let it do its thing til a TDCO appears on scanner after 170 ECT.

 

[NVW]

I would move it back to where it was. IIRC use the l65 enhanced data to do the TDCO learn. "Quomack" had a pdf on doing this, I thought I had it bookmarked but can't find it. @ak diesel driver , I think Les remembers this.

 

[NVW]

Found it:

 

[schiker]

Thank you. I agree. I think my pump was too retarded to begin with and I super retarded it like someone I know.

I read ignore IPT and IPTD and could go by TDCO value: read, adjust, learn and repeat as needed to obtain proper IP time position.
If this is correct:
TDCO =-0.5 =~ base time of +3.5
TDCO =-1.5 =~ base time of +8.5
Extrapolating Those numbers as linear my starting point was
TDCO = -.09 =~ base time of +1.45 Which is out of spec if

Extrapolating and interpolating using only the TDCO number then factory base time range tolerance could be considered
TDCO = -0.25 =~ +2.25 base time
TDCO =-0.75 =~ +4.75 base time.
or ~ +3.5 +/- 1.25

So with my new understanding:
I should adjust IP mark a hair over 1mm to driver side of my original mark then I could wait til parameters are all good and TDC learn via carcode test in the 02 enhanced screen. Or I could do KOKO and if TDCO is within spec of -.25 to -.75 I should be ok in regards to timing.

 

[FellowTraveler]

I had always used Medium Duty 02 for all my carcode settings and tweeks............

 

[THEFERMANATOR]

Your tdco of -.09 was pretty close. Your pump needed to move about the thickness of a dime to advance it into the -.25 to -.75 range. Most recommend going to the -1.25 to -1.50 range for a good compromise of power and quiet.

 

[schiker]

I can see why this engine got such a bad wrap and so few shops were able to work on it successfully. It took me a couple of tries to catch on.
To be fair Carcode confuses me. Not sure I cleared codes correctly once or twice. I do it from status window and again from enhanced but enhanced status doesn't seem to be PCM and its labelled fuel trim so still unsure about that. One adjustment TDCO did not set like anticipated on one adjustment when base time read 5.6 tdco was 2.x

I am not going to max performance I am looking for best and smoothest control of idle.

I finished up with these numbers:

while in timeset
IPT 3.6
IPTD 0.0
TDCO -.97

disable tests

just reading

IPT 12.2
IPTD 12.3
TDCO -.97

Truck cranks fine, sounds fine, and drives fine. I feel better I know its close to spec after changing to timing gears.

I still get more shimmy on launch when its cold vs warm but am not suspicious it is timing anymore.

Thanks for the help guys.