[TheRegalGS]

Yo LTG family! Can't get legitimate answers from my Buick forum so I figured I find LTG enthusiasts to help. I searched all post pertaining to misfires...can't get any clarity.

Vehicle Information:
2016 Buick Regal GS LTG - 56k - Trifecta Advantage Tune - Injen Intake

Chasing a misfire that started about 2 weeks ago. Here's a timeline:

Noticed a small misfire at 3k-5k 2 weeks ago. Nothing serious. Toss some Techron with a full tank of 93 and drove her for a week.

On Sunday the 23rd, on a WOT to pass traffic, she sputters and I pull off the throttle immediately. No CEL, but she's not happy. Misfires around 1-2k. smoothens out with throttle. Replaced the plugs immediately on Sunday with what I could get (cheap Autolites Fine Wire Iridium), better but missing under light throttle at 1500 rpm. Gets smoother over 2k, but notice significant lost in boost.

Could it be coil packs?

Ordered OEM AC Delco coil packs and OEM AC Delco Spark Plugs.

Installed new packs and plugs on Wednesday, when I pulled out the Autolites, I noticed cylinder 2 plug was full of soot and noticeably dirtier than the other 3. I figured it was a bad coil anyway, and didn't think about it any further (more on cylinder 2). Installed the coils and plugs...better, but now missing at idle. Still no CEL.

At this point its dark, I stop, and test drive to fill up. I do a couple hard pulls, but my butt-o-meter says she's not 100.

The next morning, I go to crank her up and she's missing heavily at idle. CEL flashing and Traction light on. Scanner says P0303 (cylinder 3). Idle eventually evens out after a few seconds. Clear the code, drive her for the day, same small misfire at idle but nothing crazy. Get home, pull plug number 3 and nothing out of the norm...just that small miss at 650 rpm.

I decide to reflash the tune. No change. Giving up, I reflash the factory tune...no change. UGH.

Drive it for a couple days hoping for change and nothing...no CEL. Move coil packs to see if I can get the miss to move around...nothing. Then I decided to check the gap (with a feeler gauge) to see if theres any pre detonation that changed the gap and I find plug 2 to be full of soot. Just like the set of Autolites I installed.

I'm at a lost. I'm not a newbie by any means, but I'm still learning about these engines. Didn't expect to have to dig so much so soon.

[TheRegalGS]

Also, the hard start up the next morning and fouled plug makes me believe it's either a leaking #2 injector (funny how the CEL was P0303). I'm guessing the cylinder position is inline.

[Sith]

It sounds like it might be running on 3 cylinders. You dont feel a miss at high rpm because its not firing at all, hence the low power. I'm thinking you should do a compression test to check for the typical broken piston.

[Davescamaro]

Could be an Injector staying open or possibly a Crack in the cylinder itself.

[TheRegalGS]

Confirmed.

Cracked piston.

3 months left on the 6/70k powertrain warranty. Whew.

[Sith]

Being as you are tuned that warranty is no good. They can and will look at the ecu history and see it was tuned and void your warranty.

[95TA - The Beast]

Originally Posted by Sith

Being as you are tuned that warranty is no good. They can and will look at the ecu history and see it was tuned and void your warranty.

Unless it was tuned with the "stealth" option and returned to stock before they pulled the diagnostics.

I have talked to a couple of people that did that with Trifecta and they both had no issues getting warranty to replace their engines.

In regards to *WHY* the engine blew I am highly suspicious that people are more than likely NOT using Mobil 1 or another oil that is known to prevent LSPI (low-speed pre-ignition). If that IS the case then that is probably why the piston broke.

[Sith]

I have never heard of this "stealth" option before. I'll have to look into what that is about.

[Davescamaro]

Originally Posted by Sith

I have never heard of this "stealth" option before. I'll have to look into what that is about.

I know trifecta is called Transparency mode. I use it everytime I run a flash file or update. What the dealership will do is be against you to begin with. They will put the tune is cause of engine failure. The technician has to prove that your ecu variables that were changed is cause when dealing with warranty. Just remember, don't go in there and say "oh yeah, it's tuned". Let them figure it out if you can't put it back to the stock file.
I worked at dealerships and we never say much when they are tuned unless it has to do with engine failed. They have to show warranty or tech line the different tables and in most cases a tech doesn't know the stock ones.
I hope they are on your side. If they refuse, go to another dealership. There are a few that can work with you or do a goodwill engine.

[TheRegalGS]

Two weeks at the dealership and got it back.

No tune trace on the PCM. But I also swapped back all the OE parts before taking it in...I mean who tunes and Buick, right?

Confirmed cracked piston and ring. Rebuilt engine and feels like a new car again.

Undecided if I should flash the tune again and put everything back because I actually like the car stock...for now.

[Spaceme1117]

I would not put the Trifecta tune back in as it is likely the cause of the cracked piston.

2011 Chevy Cruze I used to have. Trifecta tuned and not long after, 3 cracked pistons. Returned car to stock and new engine under warranty.

[TheRegalGS]

Originally Posted by Spaceme1117

I would not put the Trifecta tune back in as it is likely the cause of the cracked piston.

2011 Chevy Cruze I used to have. Trifecta tuned and not long after, 3 cracked pistons. Returned car to stock and new engine under warranty.

Agreed. I looked back at my logs. Tuned at 41k, blown piston at 56k. I was lucky I was able to get a rebuild under warranty with only 3 months left to go.

Are guys blowing rings and pistons without a tune? I see issues here and there...