1st data log (OBD1) and went 7000 Knock count! Any advise appreciated - log attached

I am new to tuning/logging so could use some advice as I don't know what the values for most settings are supposed to be so can't tell what clues are being given in this data log. I had to just take a section of the log to keep the file size in limits but it has examples of the knock count building up and being slightly retarded.

This is for a 95 K2500 HD 5.7 TBI. All stock. PCM = 16197427 using $0D A217 ADX. vehicle feels like its running perfectly so I was surprised. Truck is a daily driver and my only goal is engine longevity. It's got 244k and I want to get to at least 400k. Everything is in very good to excellent condition and has been well maintained. I'm concerned that this high knock count will hurt my longevity goal.

Any advice of what this log is saying would be very much appreciated! I know its a lot to ask to get a diagnosis but I really don't know how to interpret the values for the various readings.

Thank you for any help...

Soooo...your knock counter seems like it's continuously accumulating? IIRC You need to modify the bin so it's not displaying battery volts.

http://www.gearhead-efi.com/Fuel-Inj...o-knock-counts

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Originally Posted by stew86MCSS396

Soooo...your knock counter seems like it's continuously accumulating? IIRC You need to modify the bin so it's not displaying battery volts.

http://www.gearhead-efi.com/Fuel-Inj...o-knock-counts

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Thanks for responding. However this does not fit my symptoms. In my case it appears to be a true case of Knocks. Counts go up by a few hundred, retard goes on a few degrees for a few seconds and tapers off quickly runs a few minutes, Counts jump up a few hundred more, etc, etc. In a short 5-10 minute drive it will accumulate 4000-6000 counts and seemingly normal retard efforts of only a few degrees. Just wondering what is causing the unusually large number of knock counts.

Haha sorry disregard...last time had this issue it was attributed to having the wrong knock sensor installed.

Is this engine purdy much stock or does it have anything aftermarket that would require altering the stock tune. i.e. heads, cam, intake

Try posting the entire datalog in xdl format if you can. Well I did spend some time looking at attached spreadsheet... Is your base timing set to what it's suppose to be in the bin? Take out couple of degrees of timing and retest. It also appears you're lean in certain areas.

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Originally Posted by dharris894

Thanks for responding. However this does not fit my symptoms. In my case it appears to be a true case of Knocks. Counts go up by a few hundred, retard goes on a few degrees for a few seconds and tapers off quickly runs a few minutes, Counts jump up a few hundred more, etc, etc. In a short 5-10 minute drive it will accumulate 4000-6000 counts and seemingly normal retard efforts of only a few degrees. Just wondering what is causing the unusually large number of knock counts.

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didn't look at your log, just a few thoughts

your analysis and logic sounds good. knock count followed by retard followed by the knock count increment stopping is usually real knock. if the knock counts are real, carbon buildup in the combustion chambers or poor fuel quality would be the first things to look at. another reason would be more aggressive timing than your particular engine or vehicle can handle (running a light truck tune in a bigass truck engine swap)

but keep in mind very subtle momentary false knock can behave the same way, just because it disappears after timing is retarded doesn't mean the timing retard caused it to dissapear (cause and effect)

a few hundred knock counts happening randomly is typical of false knock..

the conditions during which the knock counts occur is very important as well. is TPS% or MAP increasing during the knock events? if so, they are probably real. if you are cruising or in decreasing load when it occurs, i'd be doubting their authenticity.

keep in mind too, sometimes its not an internal engine problem. something as stupid as a loose exhaust pipe banging on your floor pan can resonate to the engine and cause knock counts (and in some cases the timing retard removes enough torque to relax the engine mounts and stop the banging, really throws you for a loop)

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Originally Posted by steveo

didn't look at your log, just a few thoughts

your analysis and logic sounds good. knock count followed by retard followed by the knock count increment stopping is usually real knock. if the knock counts are real, carbon buildup in the combustion chambers or poor fuel quality would be the first things to look at. another reason would be more aggressive timing than your particular engine or vehicle can handle (running a light truck tune in a bigass truck engine swap)

but keep in mind very subtle momentary false knock can behave the same way, just because it disappears after timing is retarded doesn't mean the timing retard caused it to dissapear (cause and effect)

a few hundred knock counts happening randomly is typical of false knock..

the conditions during which the knock counts occur is very important as well. is TPS% or MAP increasing during the knock events? if so, they are probably real. if you are cruising or in decreasing load when it occurs, i'd be doubting their authenticity.

keep in mind too, sometimes its not an internal engine problem. something as stupid as a loose exhaust pipe banging on your floor pan can resonate to the engine and cause knock counts (and in some cases the timing retard removes enough torque to relax the engine mounts and stop the banging, really throws you for a loop)

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Thank you for the thoughts. I do think they are real. I checked and they almost always occur when the MAP starts going up.

The question is why? I get one possibility is carbon although I have seafoamed once. Here is a question - my O2 data is swinging wildly from less than 1oo to over 900. I know it goes back and forth across 450 but is it normal to swing to the extremes or is this a clue? is the sensor bad or is the emissions really swinging like that? if its the O2 sensor would that cause the knocks or is this unrelated?

Thanks for the help...

Reread 1st post my apologies for missing the pertinent details. Swinging O2 in closed loop is normal. What I did notice is the CTS never goes over a 100 and thus commanded afr is less than stoic. BLMs start at 128 and climb to 140. Suppose this lean condition is the cause for knock retard???

when you hit the gas, map drops, and then you see knock, does your o2 voltage swing low or high? (if it's lean knock it might swing low)

engines usually have to go pretty damn lean to cause lean knock under light to moderate load.

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Originally Posted by steveo

when you hit the gas, map drops, and then you see knock, does your o2 voltage swing low or high? (if it's lean knock it might swing low)

engines usually have to go pretty damn lean to cause lean knock under light to moderate load.

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It seems like the O2 continues to go up and down like normal. Doesn't swing and stay more lean-ish. It really feels like it's engine "load". I drove home with a heavy load in back today and got 20000 knocks. Still didn't hear or feel anything. Feels like it's running fine. But with the extra weight going uphill the engine loaded up and the knocks counts added up. I'm getting lower on gas and soon will be able to try high octane and see if it improves.

If nothing changes would that point to false/bad knock sensor? or will higher octane not automatically make some difference?

Quote:

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Originally Posted by steveo

when you hit the gas, map drops, and then you see knock, does your o2 voltage swing low or high? (if it's lean knock it might swing low)

engines usually have to go pretty damn lean to cause lean knock under light to moderate load.

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Not saying this is the problem but wanted to share. Caballero tbi 4.3l ecm '6868 plug n play '747 swap. After massaging the ve tables 4 times and called it for the day, decided to keep the laptop hooked up and still saw some cells in the 140ish range. Climb up the Pali Highway, engine rattled like crazy. Added more fuel to those cells and the knocking went away. Considering you are ALL stock then I'd lean towards something mechanical not being right. How much fuel pressure is it putting out?

My fuel pressure is around 11 during prime and 12 while running.