Getting Misfires a Few Minutes After Starting

[nitrousgp]

Hello,

To preface, I am not claiming to be knowledgeable with tuning. I know the very basics and how to navigate the HP Tuner. That said, I recently began experiencing an issue with getting misfires about five minutes after starting the truck. Originally, I thought that I had burned through another plug wire, but when I check the usual suspects, they were fine. Started the truck and drove it around and about 5 minutes later it started throwing the P0300 again. That's the scan that's attached.

The truck is a 2013 Sierra 1500 with an iron 5.3, completely stock engine with just the rings gapped to .026" (top and bottom) and LS9 MAP sensor, VSR 80mm billet wheel T6 turbo, wastegate spring at 6-7psi currently. The engine has what I believe to be a truck 6.0 cam in it. Plugs are TR55s at .030". Also has 850cc Fuel Injector Connection injectors.
I've attached a scan that was taken yesterday. You'll notice the misfires started just after five minutes into the scan, but also, I'm not getting a KR reading or cylinder misfire counts on cylinders 6, 7, or 8. Could that be possibly causing an issue with timing which is leading to the misfires? I haven't been able to check the knock sensors or wiring yet, but plan to tomorrow.

As a side issue, I'm having trouble with the truck dying at idle when warm and in park. It will start to oscillate and then die. Idles fine when warm in gear. I've played around with idle RPM setting, base minimum airflow, and overspeed/underspeed timing, but haven't quite been able to smooth the idle out yet.

Any help would be appreciated.

Thanks.

MISFIRE.hpl
5.3L Tune.hpt

[Sjd6795]

Swap to some copper plugs BR7EF gapped at 0.028 out of the box.

[blindsquirrel]

It's pulling ~25% fuel at idle. Fix the airflow model (edit: or the rich condition) and a bunch of other issues will go away.

Is it really at 20% throttle angle just to idle at 850? Is the TB all coked up or something? Actually, I see (SAE) channels being used. Don't do that on ETC GMs. Use the non-generic PIDs.

The unknown cam comment... you 100% sure it isn't a DOD cam by mistake?

[travisty75]

Actually, I see (SAE) channels being used. Don't do that on ETC GMs. Use the non-generic PIDs.

I don't mean to hijack the thread, but can you expand on that a bit? I am using SAE channels for my logging (e67 with ETC) and haven't seen anyone else mention to not do that.

[blindsquirrel]

They just read weird, not accurate. Same for a lot of the generic channels and you won't know which ones give valid numbers and which don't until after you're in too deep and all confused. Don't use them unless you have a good reason to, and just accepting the default it offers when adding a channel isn't a good reason.

[nitrousgp]

Thank you for the replies and sorry for the delayed response. I've been busy with work and haven't really had time to work on the truck.

I swapped in some NGK TR6s a couple of days ago. The truck will idle for about 45 seconds when cold and then start to go into a death oscillation. After I fire it back up it hard starts and will go into the oscillation again almost immediately. Almost like it's related to when it comes out of start-up parameters. I think it looks like it's pulling fuel because the wideband isn't fully functioning yet because it takes a good 30 seconds or so to warm up and begin reading.

As far at the throttle position PID. I changed that and will get a cold start here later today hopefully .

[nitrousgp]

It's pulling ~25% fuel at idle. Fix the airflow model (edit: or the rich condition) and a bunch of other issues will go away.

Is it really at 20% throttle angle just to idle at 850? Is the TB all coked up or something? Actually, I see (SAE) channels being used. Don't do that on ETC GMs. Use the non-generic PIDs.

The unknown cam comment... you 100% sure it isn't a DOD cam by mistake?

I won't say I'm 100% sure, but it was a stock 3 bolt cam. I thought all DOD cams were single bolt? Or am I thinking of a VVT cam? I may just buy a new aftermarket cam and install it to rule that out.

[blindsquirrel]

Yes there are 3-bolt DoD cams. They started in 2005, the single-bolt stuff didn't come along until '07. Everything that was 24x/1x was 3-bolt as there's no such thing as a single-bolt 1x cam gear.

As I mentioned before (but hadn't yet looked at; I did just now though) fix this and your idle surge mess will go away. If you wideband told you to make this, your wideband is broken or using the wrong math.

screenshot.17-04-2022 13.56.30.png

[nitrousgp]

Yes there are 3-bolt DoD cams. They started in 2005, the single-bolt stuff didn't come along until '07. Everything that was 24x/1x was 3-bolt as there's no such thing as a single-bolt 1x cam gear.

As I mentioned before (but hadn't yet looked at; I did just now though) fix this and your idle surge mess will go away. If you wideband told you to make this, your wideband is broken or using the wrong math.

screenshot.17-04-2022 13.56.30.png

OK, I guess my next question is how would I go about adjusting the tune to let the truck idle so I can start working on the VVE table? As a side note, this tune is from a supposed reputable tuner that I've been having trouble getting any type of response from.

As far as the wideband math, I'm using an Innovate SCG-1 gauge and wideband. The math is: (V/5)+5 = lambda output and (V/.3324)+7.35 = AFR.

[blindsquirrel]

Why would the low speed/idle/non-boost areas need to be much if any different from stock and non-turbo? I would go back to stock and only make changes when collected data said I needed to.

In fact I would tune the part throttle using trims and the stock narrowbands, if the plan is to run it in closed loop with the narrowbands controlling fueling after tuning. Then you can use the trims to double check your wideband isn't telling you lies.