Cammed LC9 running like a bag of Weiners

[MB07LC9]

Alright. I know there are some very smart people on here who might be able to help me out.
​​​​​​I'm running an avalanche with the aluminum LC9 5.3l. It has the following engine mods.

Texas stage 3 high lift truck cam 216/220 with the 0.600 lift and 110 LSA
Stage 2.5 ported heads by Texas speed as well.
Fast lsxrt intake manifold 103mm with fast lsxrt bullet fuel rails.
​​Nick Williams throttle body 102mm
Long tube speed engineering headers with a true dual 3 inch exhaust system
Aus injection 44# injectors.
Enclosed aftermarket cold air intake

I may be missing a few small things. But those are the major mods. I had it dyno tuned in June of 2022 and it ran great until It went to the shop a couple weeks ago where they fixed a couple small leaks around the oil pan and oil filter housing. They also fixed a leak on an aftermarket derale remote trans cooler.

They swear up and down that they didn't touch the intake manifold in any way, they dropped the front diff to repair the leaks on the oil pan and filter housing. They also tried cleaning the throttle body to see if it would help but didn't clean up the idle at all. I'm not trying to pin anything on the shop, just want my truck running well again.
​​​​​​
It immediately runs lean (higher then my aem wideband reads) when I fire it up and it chops like it's got a monster cam in it. After it's ran for a minute or so, it starts trying to add fuel. Usually around 29% on the ltft but the stft stays hovering around +/- 2%. After its done adding a ton of fuel the wideband reads normal but it reeks like pure gasoline. I've tried doing a leak test on the intake manifold (smoke machine without uv dye) I didn't notice any leaks at all. I also tried reuploading the tune from when it was dynoed and still runs like a bag of ass.

Anyone have any recommendations? Where do I go from here. My maf is reading 7g/s at idle and responding appropriately when under load or revved. My map is reading around 42 kpa. Tried unplugging them once at a time with minimal change in afr. It runs pretty decent under load and wideband is at 14.5-15.5 afr once or starts throwing a ton of fuel in the mix but it doesn't seem like it's getting burnt judging by the smell.

Im far from a tuner. Just trying to make sure I'm not missing something simple. I have the full vcm file to just not sure how to upload on here.

Thanks in advance
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[kevin87turbot]

Alright. I know there are some very smart people on here who might be able to help me out.
​​​​​​I'm running an avalanche with the aluminum LC9 5.3l. It has the following engine mods.

Texas stage 3 high lift truck cam 216/220 with the 0.600 lift and 110 LSA
Stage 2.5 ported heads by Texas speed as well.
Fast lsxrt intake manifold 103mm with fast lsxrt bullet fuel rails.
​​Nick Williams throttle body 102mm
Long tube speed engineering headers with a true dual 3 inch exhaust system
Aus injection 44# injectors.
Enclosed aftermarket cold air intake

I may be missing a few small things. But those are the major mods. I had it dyno tuned in June of 2022 and it ran great until It went to the shop a couple weeks ago where they fixed a couple small leaks around the oil pan and oil filter housing. They also fixed a leak on an aftermarket derale remote trans cooler.

They swear up and down that they didn't touch the intake manifold in any way, they dropped the front diff to repair the leaks on the oil pan and filter housing. They also tried cleaning the throttle body to see if it would help but didn't clean up the idle at all. I'm not trying to pin anything on the shop, just want my truck running well again.
​​​​​​
It immediately runs lean (higher then my aem wideband reads) when I fire it up and it chops like it's got a monster cam in it. After it's ran for a minute or so, it starts trying to add fuel. Usually around 29% on the ltft but the stft stays hovering around +/- 2%. After its done adding a ton of fuel the wideband reads normal but it reeks like pure gasoline. I've tried doing a leak test on the intake manifold (smoke machine without uv dye) I didn't notice any leaks at all. I also tried reuploading the tune from when it was dynoed and still runs like a bag of ass.

Anyone have any recommendations? Where do I go from here. My maf is reading 7g/s at idle and responding appropriately when under load or revved. My map is reading around 42 kpa. Tried unplugging them once at a time with minimal change in afr. It runs pretty decent under load and wideband is at 14.5-15.5 afr once or starts throwing a ton of fuel in the mix but it doesn't seem like it's getting burnt judging by the smell.

Im far from a tuner. Just trying to make sure I'm not missing something simple. I have the full vcm file to just not sure how to upload on here.

Thanks in advance
​​​​​​

That's an odd scenario. It's going to be difficult to diagnose without a datalog. If you click the "Go Advanced" button instead of the "Quick Reply" button, it'll give you the option to attach your calibration file and a datalog.

Are both banks adding the same amount of fuel? Do you have any exhaust leaks?

[MB07LC9]

Tried adding 5% across fuel table last night just to see if it would run a bit better (my logic was if its trying to constantly add between 19-29% fuel in the long term trims, maybe it would drop to 15-25% and Id know I'm on the right track.. this was not the case at all. wouldn't even start up ill say it again.. I'm not a tuner by any means

Ill also add that I reverted back to the original tune after it wouldn't start. I also smoked out the intake manifold for a second time last night just to verify there were for sure no intake leaks. No exhaust leaks either and it looked like all the harnesses were in decent condition and plugged in.

DO NOT DELETE. DYNO TUNE.hptLTFT ISSUE.hpl

[Alvin]

In the flex fuel section of your tune you will see something that says "Virtual Flex".. Yours is on.. This causes all kinds of dumb issues like you are describing.. Basically if the ECM is seeing lean or rich often it ASSumes the ethanol content has changed. So if it's lean for a while it will assume it has some ratio of ethanol/E85 in it. This causes all kinds of tuning headaches.

Turn virtual flex off and tune it one more time and you should be good to go.

[edcmat-l1]

Any time anything is running that lean first logical diagnostic step is to check the fuel pressure.

[MB07LC9]

Any time anything is running that lean first logical diagnostic step is to check the fuel pressure.

Fuel pressure (on the rail mounted mech gauge) is sitting at 55-60psi.

[GHuggins]

Turn off ethanol like Alvin pointed out and then play with the ect based injection timing for cold start temps. Might even want to adjust injection timing in general then fine tune using the ect table AFTER the main injection timing is close.

I see this problem a lot with big cams Injection timing will usually fix 80 or so percent on it's own. Basically your fuel IS going straight out the exhaust. I had one customers car kill some of the grass in my yard where he parked it and I fired it up the first morning to check it out because his was the same way - raw fuel straight out the exhaust.

[MB07LC9]

Thank you for the reply. Tried turning off the flex fuel (first switched it from virtual to sensor then disabled the master flex fuel entirely) still runs very lean in open loop and starts throwing 29.7% fuel in the ltft to make it run in the 14-15 afr range. But to your point. Yes. I'm pretty sure there is raw fuel being dumped out the exhaust.

I appreciate you sharing the tips about injection timing and trying to map it out with the engine coolant temp but you're essentially speaking a foreign language to me so I have it booked in next week for it to go up on the dyno again.

I'm not familiar with the hptuning software don't want to mess anything up. I just wanted to know if there was something simple I was overlooking. I appreciate your time guys!

[gtstorey]

Fuel pressure (on the rail mounted mech gauge) is sitting at 55-60psi.

There has been a pretty lengthy discussion on here on why permanently mounted rail pressure gauges shouldn't be trusted and should be verified with a diagnostic fuel gauge. If that is what you meant by "on the rail mounted mech gauge". I think blindsquirrell was the one that posted it.

[MB07LC9]

Yep. That is what I meant. I'm running bullet fuel rails and it is permanently mounted there. I had no idea they were not trustworthy; ill have to give that a read.

[Alvin]

Thank you for the reply. Tried turning off the flex fuel (first switched it from virtual to sensor then disabled the master flex fuel entirely) still runs very lean in open loop and starts throwing 29.7% fuel in the ltft to make it run in the 14-15 afr range. But to your point. Yes. I'm pretty sure there is raw fuel being dumped out the exhaust.

I appreciate you sharing the tips about injection timing and trying to map it out with the engine coolant temp but you're essentially speaking a foreign language to me so I have it booked in next week for it to go up on the dyno again.

I'm not familiar with the hptuning software don't want to mess anything up. I just wanted to know if there was something simple I was overlooking. I appreciate your time guys!

As I said before you will have to retune now that virtual flex is off. Having virtual flex on will have you chasing your tail tuning.

You should be fine with stock injection timing on this for now. Work on the basics first.

[blindsquirrel]

Is it 55, or is it 60? Does it vary between the two? Does it change on its own or only in response to throttle blips/load? Because that's a pretty big range, almost a 10% change.

Underhood-mounted permanent gauges are for decoration, not diagnostics. Liquid filled gauges especially are extremely sensitive to both temperature and barometric changes, and there can be huge swings in both of those under the hood. A real gauge that can be trusted for diagnostics lives in a quiet, protected place in your tool box and only comes out when needed to do spot checks then gets carefully stored away again.

[MB07LC9]

Guys I apologize for my ignorance here. I have no idea how to tune vehicles. Even something as simple as "working on the basics" is something I take my vehicle to a dyno for and give him a pile of money to do.

It's a waste of money. I know.
I do have a week before Its booked with the tuner. Maybe I'll start watching some YouTube videos on the basics and see if I can mess it figure it out.

Either way. Thanks for all your help and if anyone has any books or YouTube videos they recommend on basics feel free to send em my way. I'll give it the old college try.

[MB07LC9]

First off. I love the bio 😂

Second. As soon as I read the "temperature" part of your post, I felt like slamming my head into a wall. I live in northern Canada. That liquid is probably solid ice when the engine isn't running.

As per your 55 or 60 psi question, its usually around 60 psi when running but was dwindling down to 55 when not running.

[blindsquirrel]

Well temperature matters more because of the way that changes the pressure inside the gauge case, and liquid filled gauges are normally sealed or else the silicone fluid would leak out. If you took an air nozzle and put 60psi into the case, and had 60psi being measured in the rail, the needle would read 0psi. Repeated heat cycles from hot to cold, like what happens every time the car is driven and then shut off and cools, can pump ambient air into the gauge case and accumulate over time, seen it happen on my own stuff. The rubber plug that's supposed to seal it up instead acts like a one-way check valve - lets air in, but not out.

If you somehow had a partial vacuum (meaning, less than actual barometric pressure) in the case, the needle would read higher than actual.

[SiriusC1024]

You're supposed to clip the nipple on the seal so pressure equalizes with ambient. I twist and peel it off with needlenose. This gets accurate gauge pressure. They're meant to be oriented vertically when installed. The seal is there so that fluid doesn't leak out during shipping, storage, handling.
gauge.png

[edcmat-l1]

Looking through your specs I see long tubes and 3 inch exhaust. Nothing about cats. Is this a cat LESS vehicle? That combined with the cam will be your raw fuel smell. Injector timing will help some. Cats will help more.

[MB07LC9]

I expect a bit of fuel smell, but not to the extent I'm getting right now. It wasn't anything like this when it was dyno tuned and the cats were not in there then either.

No argument just don't think the amount of fuel im smelling is from the lack of cats

[edcmat-l1]

I expect a bit of fuel smell, but not to the extent I'm getting right now. It wasn't anything like this when it was dyno tuned and the cats were not in there then either.

No argument just don't think the amount of fuel im smelling is from the lack of cats

I know I'm gonna sound like a jerk here, but this is another "nah that ain't it" post. Happens on here every day.

[MB07LC9]

Nope. You dont sound like a jerk
I've owned this thing for a while and it's been running the same cam for a few years. None of these mods are new, everything's been "as is" for a couple years now. So while I appreciate you sharing your knowledge, I also know how it was before, and how it's running now.

I barely think it's a coincidence that right when it starts running like garbage that I notice the smell of fuel. I've been wrong a few times before, and I'm willing to put money down that I will be wrong again. When it goes on the dyno again and gets properly tuned, I'm man enough to update you, I'm sure my wife will tell me her thoughts on if it smells worse or not as well..

Either way. Thanks for your thoughts on it!