Knock Count

[MIHELA]

Are you seeing knock counts, or actual knock retard? The knock counter logic is strange and hard to understand. I would only worry if you see a lot of knock retard. I set up a histogram in my datastream to watch the advance, rpm, map, and knock retard. As I have been tweaking AE and PE from the base tune I would see spikes at high MAP, up to 4 degrees and I have them virtually eliminated now. A small amount on occasion of 1-2 degrees during abrupt throttle changes is normal.

 

[Stokes1114]

First step is to make sure it's real knock and not something else causing the knock sensor to report.

 

[koolbreeze]

Thanks for the help guys. I've not been able to locate knock retard in TunerPro RT. Maybe it's missing from my ADX file or I don't understand how to determine it. Can any of you help with that?

There is a "Knock Count" listed in TunerPro and that's what I was referring to. It will increment 2-6 at cold start up, which I understand is normal. Over the long weekend I took it for a couple drives and logged the data stream. It was recording occassional knocks going down the interstate with relatively no grade at around 75 MPH with the cruise set. When I got in the throttle pretty heavy the knock counter would increment 6 to 10 times in a few seconds. But I can not actually hear any knocking or pinging.

I found a test procedure for testing the knock sensor and ran some of those tests this afternoon. At idle and 1500 RPM, the engine does not knock and the knock count does not change. If I tap on the right exhaust manifold, knock count increments every time. That's as far as I went, since the chart indicates the ESC system is functioning correctly.

My timing light is a Harbour Freight special, so I'm not sure how accurate it is. I'm going to try and verify the timing with another light and a piston stop as soon as I get a chance.

I replaced the EGR valve a couple years ago, but I can't remember if I used an aftermarket or Delco valve. I intend to test it and make sure it's working correctly though.

Based on my the data logs, the TPS seems to be working correctly. I'm not that familiar with the MAP and IAC sensors on these trucks, so I need to study up on what I should be seeing from them.

I also intend to pull the plugs and see what they look like and look inside the combustion chambers as best I can with a borescope. Also going to check compression while I'm at it.

I bought a bottle of Techron this weekend that I will put in some high octane ethanol free gas and see what that does.

The throttle body has never been rebuilt and has the original injectors that have never been cleaned. I did ohm them out today though and got 1.7 ohm on each one. They are both spraying what looks like a good cone to me, but I'll probably still send them off for cleaning as soon as I can do without the truck for a couple weeks.

 

[koolbreeze]

First step is to make sure it's real knock and not something else causing the knock sensor to report.

I can't actually hear any pinging or knocking (unless I lug it in a higher gear). I'm pretty sure the knock sensor is working correctly after testing it this afternoon. What else could it be?

It does have an exhaust leak on the left side at the rear of the manifold and at the donut. I verified that today with smoke through the 02 sensor bung. But I doubt that's causing the knock sensor to fire.

 

[pro17]

Are you sure it doesnt have like a custom chip? which advances the timing at higher RPMs and you just need to fill up on premium.

 

[Stokes1114]

It could be anything on the truck making a noise that sets the sensor off. Exhaust leaks are notorious for that. I would pull timing from the whole table and test drive to see if the knock counts go down. Drop 3 to 5 degrees everywhere. If no help drop a bit more. You can essentially rule out timing that way. Also figure if the is anything under the truck making noise that may be loose. I would also clean the motor with water and not sea foam as others have mentioned.

 

[koolbreeze]

Are you sure it doesnt have like a custom chip? which advances the timing at higher RPMs and you just need to fill up on premium.

Well I bought the truck used with 90k on it, so it's possible. I've never had the cover off the ECM. According to the sticker on the ECM, it's a 16196396 with a BDUY bin and my understanding is it doesn't have a memcal (G2 I think?). So I should be able to tell if it's been de-soldered.

I've got another timing light and a piston stop on the way, just to double check the timing. I also tested the EGR system yesterday and that seems fine.

I've also noticed that it runs a little rich when the vacuum is low and the MAP kpa is high. Here is a snapshot of the BLM history table from a few days ago.

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[pro17]

So it's running rich (not by a whole lot though). Maybe it is time for a TB cleanup and injector replace. I did that on my truck (back before the TPI conversion) and it helped a lot.

 

[koolbreeze]

So it's running rich (not by a whole lot though). Maybe it is time for a TB cleanup and injector replace. I did that on my truck (back before the TPI conversion) and it helped a lot.

Yes. That’s on my list to do. But I’m wandering if the exhaust leak is also contributing. It’s leaking between the manifold and head at #7 right above the O2 sensor and also at the flange right below it. Neither are that bad yet though. I’m not going to tackle that until a couple months when I don’t need the truck every week, and not looking forward to it. There is no telling what that will end up involving. The very back manifold bolt is broken off and it appears to be broken close to the head. Sure hope I don’t end up needing to pull the dang head over it. If so, might as well pull them both and rework the top end. Then again, for what that could end up costing, I might could stick a crate engine in it.

 

[koolbreeze]

I checked the timing with another light this afternoon and the base timing is just about dead center 0 with the ESC wire unplugged.

But I noticed something I'm not sure about. I decided to check how much advance it has with the ESC wire plugged back in, so I turned the truck off, plugged wire back up, started the truck and check it again. With the wire plugged in, the timing never stablizes. It constantly fluctuates 6 to 8 degrees, making it difficult to know exactly how far advanced it is. It looks to be around 20-18 degrees, but as I said it fluctuates 6 to 8 degrees. If I give it a little throttle it will stablize for a second or 2, and then goes back to fluctuating. Is that normal?