96' L31 timing and crank relearn

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BPR Speed

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Today I attempted to use Dash Command to set timing on my truck. During my set-up of the software I scrubbed the codes and had a crank shaft correlation code so I know that's needed. I deleted the code and will in the near future run the truck to relearn the code with out a scanner.

I purchased extended PIDs in the software to gain access to the cam retard functions. Nothing descriptive on the PID name is exactly what I'm looking for but it is showing timing. I've attached a few photos for reference of what I saw on the truck. When running the truck up to 1100-1200 rpm in neutral the degrees stay at 25* it does not change when rotate the distributor in either direction. I gave it a good amount of movement clock wise and counter clockwise with no change. One PID reads -25* and the other reads 25*

After clearing all the codes I took the truck out for a drive. The following degrees is what I noted:
->Idle 17-20*
->Cruise 1000-2500 rpm 25* @ part throttle up to 35% throttle
->WOT 13-17* @ 50% to 100% throttle (2800-4800 rpm pull)

Truck runs good but this whole box of worms was opened due to a occasional pop at cruise that felt like the ignition was overly advanced.

Truck is currently on a flashedblack box PCM that has the L31 file loaded *no tables changed, post cat O2 sensor and and EGR functions deleted, whipple S/C at 4.2 PSI, GM-HT383 cam, 1.6 roller rockers, forged FM pistons, walbro 450 fuel pump. Whipple piggy back computer is working and the ignition is a MSD 6AL ignition system for the vortec L31 engines.

Anybody have such ignition timing in their trucks like this? I fully expected the ignition to be more linear in changes and not just stay at 25* then jump down to 13* under hard load. Usually when tuning cars I can sweep the throttle across it's range and see the degrees of timing change linearly. Not this time.
 

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BPR Speed

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Here's some more pictures of the ignition system. I personally believe it's the crank relearn issue but I wanted to talk over what I've seen on the ignition timing.
 

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HotrodZ06

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I was under the impression you didn't relearn the cam/crank correlation on the l31, that you adjust the distributor within + or - 2°. According to a scan tool that shows cmp retard.
 

BPR Speed

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That was my goal once I started this today. I fully intended to see that timing go down if I retarded the timing at the distributor while at 1100+ rpms. It didn't move one bit in either direction. I believe there's a crank relearn on the L31 but I'm not 100% sure. I could always drive it until it comes back. I want to iron out these small bugs before I drive it too much though.
 

1998_K1500_Sub

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When running the truck up to 1100-1200 rpm in neutral the degrees stay at 25* it does not change when rotate the distributor in either direction. I gave it a good amount of movement clock wise and counter clockwise with no change.

Good. The timing is determined by the crank position sensor independently of the distributor.


Truck runs good but this whole box of worms was opened due to a occasional pop at cruise that felt like the ignition was overly advanced.

See above.

Then see this post in this recent thread (the entire thread is relevant to you):


 

HotrodZ06

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Just found a PID that shows cam retard. Initially it was showing 17 degrees retarded. Moved it to get it locked in at 0.0*-0.3* she's running good again.
Good deal and the timing isn't advanced or retarded by the distributor like a vacuum advance distributor its controlled by the PCM and ignition module. The distributor adjustment is just to correlate to cam/crank sensors.
 

1998_K1500_Sub

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Here's some more pictures of the ignition system.

I see you've got one of those "flat-top" distributor caps (that's my term for it). Looks kinda like a crab.

While I like their clean look, I've been told they have cross-fire issues more often then a the crown-style cap. Have you heard of this, or have you ever had a problem with it?

I know my 1998 has got the crown-style cap on it now. I don't know if it ever had the flat-top cap... Dad owned it when new, I got it from him around 2010.
You must be registered for see images attach
 
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BPR Speed

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I see you've got one of those "flat-top" distributor caps (that's my term for it). Looks kinda like a crab.

While I like their clean look, I've been told they have cross-fire issues more often then a the crown-style cap. Have you heard of this, or have you ever had a problem with it?

I know my 1998 has got the crown-style cap on it now. I don't know if it ever had the flat-top cap... Dad owned it when new, I got it from him around 2010.
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This is a new AC Delco unit and I haven't seen any misfires or cross firing from it. Unit has less than 4,000 miles since the engine rebuild. The wires would be my first suspicion for cross firing. That's why I bought the Taylor 8.8mm wires.
 

L31MaxExpress

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This is a new AC Delco unit and I haven't seen any misfires or cross firing from it. Unit has less than 4,000 miles since the engine rebuild. The wires would be my first suspicion for cross firing. That's why I bought the Taylor 8.8mm wires.
I could not get a year and sonetimes less than 6 months out of the Delco caps even after vacuum venting the distributor. The wires were also garbage. Even when I had stock manifolds and heat insulators the boots would crack and the spark would arc to the tin metal heatshields. Went to MSD caps, Taylor 8.8 wires and the problem vanished. I had a Taylor wire melt against the header when it fell out of the loom without me noticing. Even with headers the boots on the Taylors have been solid.
 
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