Misfiring Issues 2018 ZL1 (Cyl #3)

JustDo1nMe · 01-11-2021, 02:26 AM

Hello, hoping I can get some help or see if anyone else has had a similar issue...

My 2018 ZL1 has just about 3000 miles. It was dyno tuned with a rotofab intake, ARH headers, borla cat-back, and LT5 throttle body.

Just before winter started, I was out on a normal cruise when the car started misfiring. It through a CEL (P0303) Misfire Cylinder #3. Along with the CEL, the instrument panel displayed errors (service rear end/axel). The codes go away when the car is shut off and then turned back on but will re-trigger once the car goes over 2k rpms. Even when codes are cleared... you can tell it has a misfire in the idle.

I have not tried any trouble shooting yet.

Any feedback is greatly appreciated. Thanks in advance!

LiqTenExp · 01-11-2021, 06:29 AM

Things to look at in order of likely hood:

1) Check 2nd spark plug on the driver side from the front (#3), make sure it is fully seated, you should get 1-2 clicks out of the coil pack and 1 click on spark plug

2) Check spark plug for proper gap (make sure it didn't get dropped or something weird), swap plug to different position if issue continues to see if it follows plug and then replace

3) Check coil pack wiring, check for full insertion then remove and check for broken pin lock(s) causing recessed contacts when inserted

I've had #1 and #3 happen

PROMETHEUS · 01-11-2021, 07:07 AM

Had the same thing happen to me about 8 months ago, but Cylinder #1. Same display codes! Bad plug....replaced by dealer.

SJFGTO · 01-11-2021, 07:46 AM

Agree with above. There have been posts with similar issues which turned out to be a loose plug wire or a bad plug. I’d start there. Good luck!!!

Markoz28 · 01-11-2021, 08:39 AM

My car was misfiring too. Turns out that the plugs fouled out. They were gapped way too tight and I was not driving it hard. Changed plugs and gapped them at 32. Car drives great with smooth idle, as smooth as can be with a cam.

JustDo1nMe · 01-11-2021, 11:16 PM

Thank you guys ill try the above!

SFV1LE · 01-12-2021, 12:56 PM

Are you running a tune with E85 or straight pump gas?

JustDo1nMe · 01-16-2021, 02:35 AM

Quote:

Originally Posted by SFV1LE

Are you running a tune with E85 or straight pump gas?

Tuned on pump gas

Stephen12ZL1 · 01-16-2021, 08:09 AM

lots of bad spark plugs so start with that first...swap plugs then see if the misfire moves to the other cylinder

Alain · 01-16-2021, 03:38 PM

any updates on this?

sr71bb · 01-16-2021, 06:03 PM

Quote:

Originally Posted by JustDo1nMe

Hello, hoping I can get some help or see if anyone else has had a similar issue...

My 2018 ZL1 has just about 3000 miles. It was dyno tuned with a rotofab intake, ARH headers, borla cat-back, and LT5 throttle body.

Just before winter started, I was out on a normal cruise when the car started misfiring. It through a CEL (P0303) Misfire Cylinder #3. Along with the CEL, the instrument panel displayed errors (service rear end/axel). The codes go away when the car is shut off and then turned back on but will re-trigger once the car goes over 2k rpms. Even when codes are cleared... you can tell it has a misfire in the idle.

I have not tried any trouble shooting yet.

Any feedback is greatly appreciated. Thanks in advance!

A bad valve spring will cause an misfire. I know I have my SS over at the dealer NOW, and that was their diagnosis. The car also would give me a service stabilitrak error as well which would clear temporarily when you restarted the car. The MISS was most noticeable at idle. I was told by GM tech that GM had gotten a bad batch of valve springs and that they were going to replace them all just to be on the safe side. Had that spring BROKEN and the valve dropped, then that would have been BYE BYE motor. That's why it is so important that when you get a FLASHING engine light that you immediately get it looked at.

JustDo1nMe · 01-17-2021, 12:43 AM

Quote:

Originally Posted by Alain

any updates on this?

Not yet. I will keep this thread updated when I do.

JustDo1nMe · 03-30-2021, 02:12 PM

Quote:

Originally Posted by JustDo1nMe

Hello, hoping I can get some help or see if anyone else has had a similar issue...

My 2018 ZL1 has just about 3000 miles. It was dyno tuned with a rotofab intake, ARH headers, borla cat-back, and LT5 throttle body.

Just before winter started, I was out on a normal cruise when the car started misfiring. It through a CEL (P0303) Misfire Cylinder #3. Along with the CEL, the instrument panel displayed errors (service rear end/axel). The codes go away when the car is shut off and then turned back on but will re-trigger once t
he car goes over 2k rpms. Even when codes are cleared... you can tell it has a misfire in the idle.

I have not tried any trouble shooting yet.

Any feedback is greatly appreciated. Thanks in advance!

Hey guys just an update on this... I recently just got the car out of winter storage and did the mentioned triage steps.

Coil packs and connections seem fine but I pulled the OEM plug and it appears it might be fouled.

What do y’all recommend for replacement plugs and gaps on them for my setup?

Can'tHave2MuchHP · 03-30-2021, 02:28 PM

Guys, crazy coincidence. Exact same problem with my 2018 this week. I tested coils and wires; all good. Thought for sure it was an Injector. I moved the plug to another cylinder and the problem followed it. Replaced the plug and good as new.

01-11-2021, 06:29 AM	#2
LiqTenExp Drives: 2017 ZL1 Join Date: Jan 2017 Location: NJ Posts: 926	Things to look at in order of likely hood: 1) Check 2nd spark plug on the driver side from the front (#3), make sure it is fully seated, you should get 1-2 clicks out of the coil pack and 1 click on spark plug 2) Check spark plug for proper gap (make sure it didn't get dropped or something weird), swap plug to different position if issue continues to see if it follows plug and then replace 3) Check coil pack wiring, check for full insertion then remove and check for broken pin lock(s) causing recessed contacts when inserted I've had #1 and #3 happen __________________ 2017 Camaro ZL1 Coupe M6 (847whp Dynojet on 93) Last edited by LiqTenExp; 01-11-2021 at 07:26 AM.

01-11-2021, 07:46 AM	#4
SJFGTO Oh Oh it's Friday Night! Drives: 2018 ZL1 1LE Nightfall Gray Join Date: Jan 2018 Location: Walton Woods Posts: 1,073	Agree with above. There have been posts with similar issues which turned out to be a loose plug wire or a bad plug. I’d start there. Good luck!!! __________________ 2018 Camaro ZL1 1LE NFG; ARH 2” headers, catless mids, ARH full exhaust, Lingenfelter 18% lower pulley, ATI Harmonic Balancer, Roto-fab CAI, EE-catch can, TM ported TB, NX Lid, BMR strut tower brace. Aeroforce dual pod interceptor gauges. Tuned by Vengeance Racing!!! 644 HP @ 6250 rpm / 689 trq @ 3660 rpm Four that wanna own me Two that wanna stone me One says she's a friend of mine...

01-16-2021, 08:09 AM	#9
Stephen12ZL1 Drives: '21 ZLE A10 Join Date: May 2012 Location: Mechanicsville, VA Posts: 6,824	lots of bad spark plugs so start with that first...swap plugs then see if the misfire moves to the other cylinder __________________ '21 ZLE A10 Wild Cherry PDR 2:00.78 VIR Full 10.68@131.69 1.68 60' '17 ZL1 A10 Mosaic Black PDR/Nav 2:03.08 VIR Full 11.003@129.2 1.75 (sold) '15 Z/28 #325 Black a/c & stereo. 2:10.1 VIR Full (sold) '12 ZL1 A6 Black 10.52@131 1.55 60' 2:13 VIR Full (sold)

01-16-2021, 03:38 PM	#10
Alain Drives: 2016 Challenger Hellcat, 2018 ZL1LE Join Date: Dec 2009 Location: Northern NJ Posts: 3,003	any updates on this? __________________ 2016 Challenger Hellcat /B5 blue/Sepia interior/Brass Monkey Wheels/ 2018 ZL1 1LE/Red hot 2019 Shellby GT 350R/ Oxford white/ Matte Black Stripes/ Carbon Fiber Dash/ Electronics Package #413

01-11-2021, 02:26 AM	#1
JustDo1nMe Drives: 2018 ZL1 Join Date: May 2016 Location: Ma Posts: 112	Misfiring Issues 2018 ZL1 (Cyl #3) Hello, hoping I can get some help or see if anyone else has had a similar issue... My 2018 ZL1 has just about 3000 miles. It was dyno tuned with a rotofab intake, ARH headers, borla cat-back, and LT5 throttle body. Just before winter started, I was out on a normal cruise when the car started misfiring. It through a CEL (P0303) Misfire Cylinder #3. Along with the CEL, the instrument panel displayed errors (service rear end/axel). The codes go away when the car is shut off and then turned back on but will re-trigger once the car goes over 2k rpms. Even when codes are cleared... you can tell it has a misfire in the idle. I have not tried any trouble shooting yet. Any feedback is greatly appreciated. Thanks in advance!

01-11-2021, 07:07 AM	#3
PROMETHEUS Drives: 2019 ZL-1, Shadow Gray, Sold Join Date: Jan 2019 Location: Fredericksburg, VA Posts: 1,390	Had the same thing happen to me about 8 months ago, but Cylinder #1. Same display codes! Bad plug....replaced by dealer.

01-11-2021, 08:39 AM	#5
Markoz28 Drives: 18 ZL1 nightfall grey A10 Join Date: Apr 2018 Location: RGV Texas Posts: 1,527	My car was misfiring too. Turns out that the plugs fouled out. They were gapped way too tight and I was not driving it hard. Changed plugs and gapped them at 32. Car drives great with smooth idle, as smooth as can be with a cam.

01-11-2021, 11:16 PM	#6
JustDo1nMe Drives: 2018 ZL1 Join Date: May 2016 Location: Ma Posts: 112	Thank you guys ill try the above!

01-12-2021, 12:56 PM	#7
SFV1LE Drives: 2018 Hyper Blue ZL1 1LE Join Date: Dec 2018 Location: CA Posts: 1,365	Are you running a tune with E85 or straight pump gas?

03-30-2021, 02:28 PM	#14
Can'tHave2MuchHP Drives: Fast Join Date: Mar 2015 Location: Michigan Posts: 3,696	Guys, crazy coincidence. Exact same problem with my 2018 this week. I tested coils and wires; all good. Thought for sure it was an Injector. I moved the plug to another cylinder and the problem followed it. Replaced the plug and good as new.

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