1996 5.7 detonation, pinging, spark knock problems

[machinehead]

I have a 1996 k1500 5.7 with 234,000 mi. I have had it 21 years, so i know her pretty good. I have been driving 80 miles a day for work in San Antonio. in the mornings its about 70 and humid outside. The truck runs great. on the way home its more 95 and i have been getting some spark knock. Its mainly going up a grade when the engine is kinda chugging along and speed is slowing down. i have been scanning while driving and have noticed when its pinging my spark advance is down to -1. here are some data points. when it was doing it up a gentle long hill and the gear stayed in overdrive.

RPM 1783
Speed 62
ignition timing for #1 cylinder -.5
Air intake temp 124
throttle position 53%

i don't have many hills going to work but here is a snippet of morning. just strait away easy driving.
RPM 2022
speed 71
ignition timing for #1 cylinder -33
intake air temp 78
throttle position 26.27

I did get a p 1406 the other day for EGR pintle. i have a new delco EGR on the way. i also have some of the seafood top end cleaner that has the long hose to spray into the throttle body. i replaced the knock sensor and the connector end last weekend, that didn't change anything. i have heard the EGR can cause problems with spark knock without setting codes off. I'm going to do a top end clean before changing the EGR. the plugs, wires, cap, rotor were all changed 34,000 miles ago. the coil is original.

Thoughts???

 

[machinehead]

So i downloaded the DashCommand app that gave access to the Cam retard (CKP/CMP Correlation) i think this is the PID used to set the "Base Timing" of the distributer. if so this should be 0 +/- 2. mine is at -8.3. on this trip home i used the new app and was going up my favorite hill. it was pinging real good here.

67% engine load
7.12 knock retard
48.2 throttle position
0 missfires
106 F intake temp
1.69 spark advance
1471 RPM
52 MPH
-2.5 ignition timing advance for #1 cylinder
20 Counts KS Knock Sensor activity.

 

[PlayingWithTBI]

From past experience, low fuel pressure will cause lean conditions under heavy loads, which will possibly cause detonation. Can you log O2 feedback with cross counts? Or get a gauge and look at fuel pressure under load.

 

[east302]

So i downloaded the DashCommand app that gave access to the Cam retard (CKP/CMP Correlation) i think this is the PID used to set the "Base Timing" of the distributer. if so this should be 0 +/- 2. mine is at -8.3.

That zero degrees would be measured at 1,000-rpm. It would be good to go ahead and set it.

 

[machinehead]

i did check it at 1000RPM right as i got the app to check it. it was still right at -8 or so. it fluctuates a couple tenths of a degree.

 

[L31MaxExpress]

What are the STFT and LTFT readings when this is occuring? It is possible it is starving for fuel when this is occuring. When was the last time the fuel filter was changed?

 

[machinehead]

Well I just had to change out the fuel pump. It gave up on me. I did run it out of fuel a week earlier. That prolly did it in. I put in a new Delphi assembly. It still did it today going up a long grade. Spark advance ran down to 4.5. I did adjust the cam position sensor to 0. I also changed out the EGR valve as I was getting a code for that. I ran seafoam spray in the intake before any of this. It seems to idle better and runs nice and smooth in the morning. Just a bit of pinging when lightly accelerating or going up a grade. I can drop it to 3rd and it goes away or get on it and it goes away. I prolly haven’t changed the fuel filter in like 10 years. I can take it up to 5k and accelerate to 100 so I don’t think it’s starving for fuel.