Help - Time set and TDC learn

[Chief915]

All, I have searched the forum and "think" I am doing these processes correctly, but I am coming up with odd results. Let me know if I am missing something here.

This is the thread that I am going by.... post #2 http://www.thetruckstop.us/forum/showthread.php?11754-FYI-TDCO-Timing-the-DS4-Injection-Pump

94 Suburban, "F" engine, 5068 IP with stock BMSD chip, new Bosch injectors, and I am using GMTD scan tech.

Here is a snapshot of before I touched anything.

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ENGINE SENSORS
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Engine run time: 00:13:02
Boost pressure (MAP): 14.4 PSI
Desired EGR: 15.23 PSI
Desired idle: 600 RPM
EGR pressure: 15.01 PSI
EGR duty cycle: 0 %
Engine coolant temp: 186.4 F°
Engine speed: 581 RPM
Glow plug relay feedback: 0.1 Volts
Glow plug voltage: 0.1 Volts
Ignition voltage: 13.2 Volts
Wastegate duty cycle: 67.2 %

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INFORMATION SENSORS
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PCM Calibration ID: 145
Current DTCs: 0
Accel. ped. pos. 1: 0.67 Volts
Accel. ped. pos. 2: 4.41 Volts
Accel. ped. pos. 3: 4.02 Volts
Barometric pressure (BARO): 14.15 PSI
Battery voltage: 13.3 Volts
Fuel temperature: 104.7 F°
Intake air temp: 96 F°
Throttle position: 0 %
Turbo boost (Calculated): 0.25 PSI
Voltage reference sensor: 1.3 Volts

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INJECTION PUMP SENSORS
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Actual injection pump timing: 25.78 Deg °
Cam reference missed: 0 Counts
Crank reference missed: 0 Counts
Fuel calibration: 125 Counts
Fuel rate: 9.38 mm³
Fuel rate - Cruise: 0 mm³
Fuel rate - Idle: 9.38 mm³
Fuel rate - Maximum transient: 35 mm³
Fuel rate - Throttle requested: 0 mm³
Injection pulse width: 2.22 ms
Injection timing - Measured: 4.4 Deg °
Injection timing - Desired: 4.4 Deg °
TDC offset: -0.35 Deg °


Now, I have read on various posts that when you command "time set" or "tdc learn" the engine could/would/should stumble, change sounds, etc while the processes are running.... Is that correct? I commanded "time set" on mine and the rpm/sound/smoothness of the engine didn't change at all, almost like nothing was happening at all.

I got under the hood and rotated the IP toward the driver's side slightly. I commanded "time set" and "tdc learn" again...still no changes in engine noise or smoothness at all during the process. TDCO changed to -2.02 and set code 88.

I got under the hood again and rotated the IP back to the passanger side maybe half the width of the scribe mark, barley enough to see it move and cleared the code. Started it again and immediately got actual and desired timing of 4.5. I commanded "time set" and TDC learn, .... again no rpm change or audible change in the way the engine ran at all, either during time set or during tdc learn. No codes after it was finished.

Right now, this snapshot is where I am sitting.
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ENGINE SENSORS
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Engine run time: 00:19:50
Boost pressure (MAP): 14.6 PSI
Desired EGR: 15.23 PSI
Desired idle: 600 RPM
EGR pressure: 15.01 PSI
EGR duty cycle: 0 %
Engine coolant temp: 188.2 F°
Engine speed: 581 RPM
Glow plug relay feedback: 0.1 Volts
Glow plug voltage: 0.1 Volts
Ignition voltage: 13.6 Volts
Wastegate duty cycle: 67.2 %

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INFORMATION SENSORS
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PCM Calibration ID: 145
Current DTCs: 0
Accel. ped. pos. 1: 0.69 Volts
Accel. ped. pos. 2: 4.41 Volts
Accel. ped. pos. 3: 4.02 Volts
Barometric pressure (BARO): 14.15 PSI
Battery voltage: 13.6 Volts
Fuel temperature: 98.2 F°
Intake air temp: 87.6 F°
Throttle position: 0 %
Turbo boost (Calculated): 0.45 PSI
Voltage reference sensor: 1.3 Volts

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INJECTION PUMP SENSORS
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Actual injection pump timing: 26.93 Deg °
Cam reference missed: 0 Counts
Crank reference missed: 0 Counts
Fuel calibration: 135 Counts
Fuel rate: 7.5 mm³
Fuel rate - Cruise: 0 mm³
Fuel rate - Idle: 7.19 mm³
Fuel rate - Maximum transient: 35 mm³
Fuel rate - Throttle requested: 0 mm³
Injection pulse width: 2.21 ms
Injection timing - Measured: 4.3 Deg °
Injection timing - Desired: 4.4 Deg °
TDC offset: -1.94 Deg °


Does it sound like I am doing the procedures correctly or am I missing something? Does the data look/sound normal? Is it normal that the engine sound doesn't change at all when I command "time set" or "tdc learn"....even after moving the IP? Where I am sitting right now, is that really close to "ideal", should I stop messing with it and be happy with where it is? Does this indicate anything is worn out (IP, timing chain, etc)?

I thought I read somewhere that you want actual timing around 8 to 8.5, and TDCO at -1.94 for a best case senerio.... mine timing is 4.5 and TDCO is -1.94.... how do I get the timing to advance without changing the TDCO? Will I "see" actual timing of 8.5 on my data or will it show 4.5 on the screen, but actually be 8.5 because of the new TDCO? The article I referenced at the beginning kinda confused me on these questions.....

Thanks in advance.

 

[WarWagon]

You have changed the timing from -.53 to -1.85. This is not "basically back" to where it started. You could loosen the bolts and re-tighten them and come up with a different timing without turning the pump. Most go for -1.5 as the -1.85 will clatter more in the cold morning.

Entering the modes to set the timing you may hear a change in the engine. Mine did not stumble. It was as slight of a change in sound as the extra load from the AC compressor kicking in would make. The article warns you that it can run bad while this goes on. I have new injectors and that can make make a difference.

 

[Chief915]

You have changed the timing from -.53 to -1.85. This is not "basically back" to where it started.

Agreed....

After doing the TDC learn again, I came up with -1.94. I also re-edited my original post in order to make the "before moving the IP" and "after" data more clear.

 

[NVW]

I've set mine several times and only once did it run rough, that was the first attempt after code 88 appeared.

I think buddy mentioned the act. and des. timing numbers are determined by the ecm program.

 

[Crankme69]

Yr good

 

[buddy]

There is a difference between OBD1 and OBD2 procedures. Mine never stumbles unless I purposely retard the timing way too much. OBD2 trucks may go to a high idle, and someone I think assumed it was so it wouldnt die, but I have never had a problem, even at under 600rpm idle.

The desired and measured timing under normal conditions are completely determined by the ECM program. You have the stock programming for a 5068 IP, and the timing curve kind of stinks. Your truck would feel twice as powerful with just a more advanced timing curve. GM wised up and did make idle timing 8.5 degrees for all of them starting in 95, some of them in 94. GM advanced it even further with OBD2. So if you get an aftermarket chip it will really help your throttle response and potentially better economy around town. Its these trucks that have the most to gain for a new program.

 

[Chief915]

You have the stock programming for a 5068 IP, and the timing curve kind of stinks. Your truck would feel twice as powerful with just a more advanced timing curve. So if you get an aftermarket chip it will really help your throttle response and potentially better economy around town. Its these trucks that have the most to gain for a new program.

That's actually really good news..... I had planned on getting a chip at some point in the future anyway.... So with what you said, I will get the most bang for the buck out of a new chip.

Thanks for the explination, it really cleared things up.