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.
