Code 0306 cyl 6 misfire
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Code 0306 cyl 6 misfire
This is on my C7 RedVert
Was traveling to Lake Placid this morning on I87, had just gunned it a little to pass someone at about 70 mph when the car starts shaking and suretrack service shows in DIC and then engine light starts flashing. BTW, when idling in gear there is a definite miss like a cylinder went dead. I was able to thankfully drive it 80 miles back home. Checked codes and all i get is P0306 #6 cylinder misfire. So I go to the passenger side 3rd coil back and check and spark is really strong and plug wire appears OK. Next will check fuel injector at # 6, first with noid light then impedance in coil.
Was traveling to Lake Placid this morning on I87, had just gunned it a little to pass someone at about 70 mph when the car starts shaking and suretrack service shows in DIC and then engine light starts flashing. BTW, when idling in gear there is a definite miss like a cylinder went dead. I was able to thankfully drive it 80 miles back home. Checked codes and all i get is P0306 #6 cylinder misfire. So I go to the passenger side 3rd coil back and check and spark is really strong and plug wire appears OK. Next will check fuel injector at # 6, first with noid light then impedance in coil.
Last edited by 95BLKVette; Sep 24, 2022 at 09:54 PM.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
I have the full set of Helm manuals and when a P0306 sets the fuel injector is turned off for that cylinder to save the cat.
Last edited by 95BLKVette; Sep 24, 2022 at 07:39 PM.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Can’t pull the valve cover until next week to check…..why do you think it’s a valve spring?
BTW, this Vert only has 36k on it!
I don’t hear any mechanical clanking, etc. either…..
Also it’s one of the AFM deactivated cylinders 1,4,6, & 7, so maybe there is an issue with the disabling lifters?
BTW, this Vert only has 36k on it!
I don’t hear any mechanical clanking, etc. either…..
Also it’s one of the AFM deactivated cylinders 1,4,6, & 7, so maybe there is an issue with the disabling lifters?
Last edited by 95BLKVette; Sep 24, 2022 at 10:59 PM.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
You can look at the resistance of the injector…don’t know what the spec is in ohms but you can see if the windings are shorted or open…only with a scope will you be able to look at the voltage waveform…a lot of these GDI engines have cold misfires with all that carbon buildup on the intake valves at startup and at around 40,000 to 50,000 miles or so but yours may be bad enough for the misfire to happen under load…having a borescope is a good way to see this buildup instead of just guessing.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
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From: Cape Coral, Florida
This is on my C7 RedVert
Was traveling to Lake Placid this morning on I87, had just gunned it a little to pass someone at about 70 mph when the car starts shaking and suretrack service shows in DIC and then engine light starts flashing. BTW, when idling in gear there is a definite miss like a cylinder went dead. I was able to thankfully drive it 80 miles back home. Checked codes and all i get is 0306 #6 cylinder misfire. So I go to the passenger side 3rd coil back and check and spark is really strong and plug wire appears OK. Next will check fuel injector at # 6, first with noid light then impedance in coil.
just found out the cylinder number is the one in the firing order so it is actually cylinder #5 on the driver side!
Was traveling to Lake Placid this morning on I87, had just gunned it a little to pass someone at about 70 mph when the car starts shaking and suretrack service shows in DIC and then engine light starts flashing. BTW, when idling in gear there is a definite miss like a cylinder went dead. I was able to thankfully drive it 80 miles back home. Checked codes and all i get is 0306 #6 cylinder misfire. So I go to the passenger side 3rd coil back and check and spark is really strong and plug wire appears OK. Next will check fuel injector at # 6, first with noid light then impedance in coil.
just found out the cylinder number is the one in the firing order so it is actually cylinder #5 on the driver side!
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Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Look at this:
Definition
P0306 is a cylinder specific misfire code, which means that Cylinder 6 is misfiring and causing it. An important thing to understand when finding the location of Cylinder 6 is that it’s going to be the sixth cylinder in the firing order. It won’t be the sixth cylinder that you might see when looking at the engine.https://www.700r4transmissionhq.com/...hevy-corvette/
After some further research, I agree that the above website is misinformed! You are correct!
Last edited by 95BLKVette; Sep 24, 2022 at 09:57 PM.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
I’m well aware of the cylinder location….
Look at this:
Look at this:
Definition
P0306 is a cylinder specific misfire code, which means that Cylinder 6 is misfiring and causing it. An important thing to understand when finding the location of Cylinder 6 is that it’s going to be the sixth cylinder in the firing order. It won’t be the sixth cylinder that you might see when looking at the engine.
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
https://www.700r4transmissionhq.com/...hevy-corvette/
That’s what I thought but then I read the above link…..
I'm going to see if it’s in the Helms manuals, because if it is, that website is very misleading!
After some further research, I agree that the above website is misinformed! You are correct!
That’s what I thought but then I read the above link…..
I'm going to see if it’s in the Helms manuals, because if it is, that website is very misleading!
After some further research, I agree that the above website is misinformed! You are correct!
Last edited by 95BLKVette; Sep 24, 2022 at 09:57 PM.
Moderator, Tech Contributor
Joined: Sep 2013
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From: Cape Coral, Florida
Helms doesn’t have very good info !!…I use Mitchell DIY and Alldata but my choice by far is Alldata…you can get a month subscription for $19.99 if that’s all you need the sub for.
Le Mans Master
Joined: Oct 2014
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From: Atlanta GA
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
https://www.corvetteblogger.com/2021...-gm-v8-models/
If an AFM lifter is mechanically collapsed/stuck, low compression will be found on that cylinder during an AFM compression test, along with a consistent valve train tick noise, SES light, DTC P0300 and engine misfires on the related cylinder.
Last edited by 95BLKVette; Sep 24, 2022 at 10:41 PM.
Le Mans Master
Joined: Oct 2014
Posts: 8,673
Likes: 2,728
From: Atlanta GA
Agreed, since this is on cylinder 6 which is one of the cylinders in the Economy mode I wonder if this is the issue with the cylinder #6 disabling lifters as there is a class action suit against GM which was filed last December!
https://www.corvetteblogger.com/2021...-gm-v8-models/
https://www.corvetteblogger.com/2021...-gm-v8-models/
Also just looking at the wire or saying it had good spark is not enought .... swap that coil and the wire with another cylinder, then go drive it like you stole it and see if the code moves to the cylinder that you swapped with , if so swap wire back ... then check it again . Also don't discount a bad plug as they will pop a tip off in a heartbeat
Make sure you put a bit of dielectric grease in the boots oboot the ends. You will now be able to feel the click when you push it on
If I was a betting man , my money is on one of the three....
Dave
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
I already checked the #6 plug wire and it’s securely attached.
I also pulled the plug wire off the coil pack and checked with a screwdriver to the block and get a very hot 1.5” spark!
I haven’t pulled the plug yet as I’m going to attempt to go to Lake Placid a second time tomorrow with our 2017 XT5 Cadillac 👍😁
Don’t worry Dave, I’m going to do a very detailed examination of this.
I’ve been wrenching on Vettes for 20 years and have 3 of them with a lift and ample tools in my garage👍
I also pulled the plug wire off the coil pack and checked with a screwdriver to the block and get a very hot 1.5” spark!
I haven’t pulled the plug yet as I’m going to attempt to go to Lake Placid a second time tomorrow with our 2017 XT5 Cadillac 👍😁
Don’t worry Dave, I’m going to do a very detailed examination of this.
I’ve been wrenching on Vettes for 20 years and have 3 of them with a lift and ample tools in my garage👍
Last edited by 95BLKVette; Sep 24, 2022 at 11:03 PM.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
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From: Cape Coral, Florida
You really need to have diagnostic and not hand tools if that what you are referring too…diagnostics is a whole different skill set than wrenching !!
Thread Starter
Drifting
Joined: Nov 1999
Posts: 1,502
Likes: 12
From: Yorktown Heights NY
Any suggestions? As I mostly do all my own work. Except inspections😁
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,621
Likes: 4,066
From: Cape Coral, Florida
Purchased a used Tech1 for my 95 coupe years ago, and it has served me well. Also have a code reader for my 2009 Vert. I used the scanner to get the P0306 DTC. Need to get a Tech 2 equivalent for my 2015 C7.
Any suggestions? As I mostly do all my own work. Except inspections😁
Any suggestions? As I mostly do all my own work. Except inspections😁
Le Mans Master
Joined: Oct 2014
Posts: 8,673
Likes: 2,728
From: Atlanta GA
Purchased a used Tech1 for my 95 coupe years ago, and it has served me well. Also have a code reader for my 2009 Vert. I used the scanner to get the P0306 DTC. Need to get a Tech 2 equivalent for my 2015 C7.
Any suggestions? As I mostly do all my own work. Except inspections😁
Any suggestions? As I mostly do all my own work. Except inspections😁
Dave
