My truck is a 1999 GMC Sierra 1500 with a 5.3l engine from an 02 Silverado. It also has a BTR Stage 2 Truck cam (212/218, .553, 113+2). Now I have been tuning the truck myself, with basic knowledge and I have the MAF and VE tables dialed in OK for what I know. I am not tuning with a wideband o2 and I'm just using the narrowband o2's as I don't have the money for it right now.
I believe I'm dealing with false knock, but not 100% sure. I've tried removing some spark and added fuel in certain situations but don't believe it helped. I originally wanted to get the 2002 tune for the added benefits and updates but haven't figured out how to exactly do it whilst keeping my VIN.
I have a log of a short drive with 87 octane fuel and I tried capturing a lot of situations. It was a warm and humid day. I also had my AC running which was an interesting thing, it kept removing spark via torque management every time it kicked in, I think. I also have two short logs on a different day it was a bit cooler and drier also without AC on. However, when I was trying some WOT stuff to see if knock was present or not I was running into I think a VERY lean condition. Another thing that happened is my injector duty cycle % was off the charts, above 100%. My truck has not acted like this ever, so something strange is happening.
So my first question is how to deal with false knock, if it exists and how to not run into real knock when attempting to fix false knock. I want to try some 100 octane fuel but haven't been able to get it since my station just ran out or shut it down for the time being. I know without a doubt I probably should desensitize the sensors just a bit since the valve train is quite loud. Since there is more knock download RPM than high RPM situations for some reason.
My next question since it popped up whilst testing for the knock issues. During WOT roughly around 3.5k+ RPM and higher or so, my o2 sensors start reading very lean, the o2 sensor voltage basically bottoms out. Another thing that happened is the injector duty cycle % went well beyond 100% usage. Neither of these things have ever happened before. My INJ Duty got close to 100% but never above, plus my o2 sensor voltage has always been 850+ MV during WOT. There is also a lack of power once I was reaching about 4.5k RPM, that's why in the logs I let out lower than my 6k shift.
Would anyone know why all of a sudden I'd be out of fuel when my truck has never acted this way before? Is it possible an injector or something is failing so then computer is asking for more fuel when there isn't any? Another thing I saw is one time my B1 o2 sensor read very low, while the B2 o2 read almost fine. However, I don't have a catalytic converter on B1 (Driver side) the passenger side still has one. The last thing I can think of is my gas tank had less than 6 gallons of fuel in the tank, probably close to 1-3 gallons, so is it possible that I was sucking air? There was NO surging of any kind during these tests except MAYBE the last 3-4 minutes of the PT 2 log but I think that was just knock retard.
I did just put an order in for some 8.1l injectors just to cover my butt with fuel and they're not large enough that I should have issues with idling or anything like that. We'll have to see how that works later on.
Tune) Build 12.2 - A safe tune with few changes to current Build 12.7. NO MAF or VE changes or Spark changes.
Tune) Build 12.7 - The current file I used to test for knock, and the one that has odd fueling issues.
Log) Build 12.2 - The safe tune with a few WOT pulls that shows the old status of how the truck acted.
Log) Build 12.7 - The log with testing 87 octane fuel.
Log) Build 12.7 c) PT 1 - Log testing some kind of 87/93 octane mix hopefully mostly 93 was in the tank with fueling issue.
Log) Build 12.7 c) PT 2 - Log still testing 93 octane, with fueling issue.