David Lively

So, I bought my 2011 base / M6 just over a year ago (4/2020) with 44k miles from a local dealer here in DFW. (Earth Motorcars - they had, among other things, a couple of McLarens on the showroom floor. Seemed like a nice place. Now, I'm not so sure about that.)

Since then, I've had a number of issues with the car. (For instance, it came with a Camaro oil pan, apparently because it came with a crate motor and the installer didn't bother swapping the correct oil pan over.) The latest issues is melting (again) the fan controller harness connector. Today, I (finally) fired up HP tuners to see what the fan control table looks like.

Mind you, it was my understanding that this is a stock car. Other than some poorly-applied tint over the tail lights and markers, some "meh" aftermarket wheels, being dropped about 1.25" all the way around and a remote clutch bleeder (which I didn't notice until recently, but it certainly raised my eyebrows), everything looks OEM.

AND THEN I started looking at the fan tables.

This is my car:

And this is from a 2012 tune from the HP Tuners repository that I'm using as a reference:



So, I thought, that's weird. So kept looking and found:

and


...
Pretty much every DTC related to the cats is disabled. Isn't that, like, highly illegal?

(Oh, and they told me that they sent it to the local GM dealer to have it "reflashed" before I took delivery, due to an intermittent rough idle. That never fixes anything, anyway, and it clearly was NOT flashed by a GM dealer.)

That's just the tip of the iceberg. There are literally hundreds of changes vs stock, including things like fuel pump voltage correlation.

I am not a tuner. I have no way of knowing what's been replaced on the car; things like MAF values, fuel pump, injector constants, etc. are all modified. I can look at the injectors and tell if they're OEM; I cannot, however, easily determine if the fuel pump(s?) is stock; the voltage changes imply that it is not.

Oh, and the car has an extended warranty, bought through the dealership. I'm really, really tempted to just take it back to them and say "Make it legal," but I'm not sure how that conversation is going to go. I've found that they're the kind of place that just says things are fixed without actually fixing them.

So, aside from my rant:

Any suggestions on getting this thing back to stock, without blowing something up?

Tune attached for the curious.

MSteel

you can download a stock tune from the HP tuners repository and just match all the values back to stock

David Lively

My concern is that if other supporting modifications are still on the car (like a different fuel pump), then setting everything back to stock might cause problems. There's one table (I can't get to it at the moment) that appears to control fuel pump voltage based on RPM, load and something else. If the pump has been swapped out to something that expects a different voltage, I could see some Very Bad Things™ happening.

On the up side, at least this isn't an OHV turbo car. Those things are super-easy to destroy.

Guess I have to start somewhere; going back to stock seems like as good a place as any.

lbzraptor

I would find a competent LS tuner in the area to look at it. Based on what they find in the tune you have and a look at the car they can probably tell you what has been done to the car. Then they can come up with a tune to fix your issues. From my understanding if someone doesn't know what they are doing with a tune they can blow a motor pretty quick.

David Lively

Brief update:

I went ahead and flashed the (hopefully) OEM tune from the HP Tuners repository. (Well, mostly - I went ahead and disabled CAGS and shifted the fan curve a little to the left, but still maxing out at 90%.)

Some observations:
- Since I bought the car last year, it's had a weird stumble every ~20 seconds or so at idle. That problem is now gone.
- I also had a weird hesitation at ~2k RPM. That has also disappeared.
- The fan no longer sound like a jet engine. It's running a little warmer than before - around 205º - 208º when parked - but nothing too concerning.
- For some reason, the idle had been set to 850. Apparently it's supposed to be 650RPM, so that has been corrected.

Overall, it's a much better-behaved car now. I wish I'd done this a year ago.

TL;DR:
Next time I buy a car, I'll bring my laptop and MPVI2 along.

phils C5 vette

So you downloaded a tune from the tune repository from someone else's car because you believe its stock, and uploaded that to your car?

Good luck with that lol

David Lively

@phils C5 vette I compared several stock tunes from the repository. Other than the VIN, they were identical. So, either they're really stock, or they've all been modified in exactly the same way.

The car is running fine. If this was a turbo motor, I'd have been a lot more hesitant, but for an NA, cam-in-block engine, you can't do that much damage.

schpenxel

You really shouldn't just flash the other people's tunes, even just for the fact that you probably wasted credits doing it and run some risk of getting some weird behavior if OS's done line up. Right way to do it is to open the stock file as a compare file and copy the differences over to yours. Regardless, it's done now.

Also, FYI, HPTuners only has stock files on their repository now. They stopped posting anything else due to EPA stuff.

David Lively

Sigh.

I didn't just flash someone else's tune. I grabbed the stock GM tune, copied the differences over to mine, and updated the car. Obviously you don't "waste credits" in that process unless you blindingly buy a license just for that file. (Though, I'm somewhat surprised how many people on the HP Tuners forums believe that you do.) (The "You do not have a license for this file" error doesn't exactly clear that up for most people but, then again, HPT is in the business of selling credits.)

I spent quite a bit of time analyzing the differences in the file I eventually went with, and comparing it to others that I found in the repository and other places. I disabled CAGS and adjusted a few other things not worth mentioning, but it's effectively stock, and running like a champ.

David Lively

Thanks for the warning, but that's exactly what I did. Why on earth would one buy a license for a file in addition to the two credits for the VIN? Seems like a waste of $100. (HP Tuners could do a bit more to clarify that process but, then again, they're in the business of selling credits.) I know a guy who, somehow, wound up paying for 3x credits because of this confusion. (And, no, it wasn't me. But I learned from his experience.)

What I have now is the OEM tune. I reviewed and merged all the changes, disabled CAGS and adjusted the fans to come on a little sooner (but still maxed at 90%; whoever put 99% in my previous tune probably doesn't understand PWM). Otherwise, it's stock. A helpful friend also sent me their stock tune for a sanity check; all is as it should be.

The car is functioning FAR better than it has since I bought it a year ago. My only outstanding concern is the LTFTs are a little off for my taste (-7% to -8%). Thinking I need to pull one of the injectors and make sure it's what it's supposed to be. Considering this thing came with a Camaro oil pan (crate motor) and has an AC line from an entirely different, heretofore-unidentified model (quite possibly also a Camaro), very little would surprise me at this point.

Sub8

I wouldn't worry about those LTFT....