P0302 misfire
Thread Starter
Racer
Joined: Oct 2014
Posts: 490
Likes: 92
From: Savannah GA
P0302 misfire
I've got a 2017 Z06. Got in the car today and started it up and it was running really rough, had the stabilitrack icon and engine icon on the dash. Ran for a few minutes and it smoothed out. Scanned for codes and had 1 pending, P0302 which a quick google search shows as misfire for prior generation corvettes. Didn't really find anything on C7. Found nothing searching the C7 forums here for this code.
It also had a Check Rear Axle message.
I took it out for a short drive and I always use Active Rev Match, as I find it smooths out both upshifts as well as the downshifts, but my shifts were as if it wasn't on for the upshifts, and when doing a 4-3 downshift it clearly was not matching revs.
Going to schedule with the local dealer to have it looked at, but figured I would post up on the forum here and see if anybody has any ideas. Car was running great on Wednesday when I drove it.
Thanks
It also had a Check Rear Axle message.
I took it out for a short drive and I always use Active Rev Match, as I find it smooths out both upshifts as well as the downshifts, but my shifts were as if it wasn't on for the upshifts, and when doing a 4-3 downshift it clearly was not matching revs.
Going to schedule with the local dealer to have it looked at, but figured I would post up on the forum here and see if anybody has any ideas. Car was running great on Wednesday when I drove it.
Thanks
Race Director
Joined: Nov 2005
Posts: 14,553
Likes: 1,548
From: Supporting the Corvette Community at Abel Chevrolet in Rio Vista, CA 707-374-6317 Ext.123
St. Jude Donor '08
We've seen a handful of injectors on the LT1/LT4 cars and they usually run worse at start up so that would be my internet diagnosis.
RICH
RICH
Heel & Toe
Joined: Dec 2019
Posts: 15
Likes: 11
From: Ingleside, illinois
Pick up my 2017 C7 ZO6 from storage last week and drove it for about 10 miles before the identical issue happen to me the engine began running rough and the service rear axle came on as well as the stabiltrack light came on. When I got home I plugged into he OBD and got the same code PO302 misfire in cylinder 2. I swapped the coils and check the plugs but no signs of any issues and it still is running rough.
2nd Gear
Joined: Jun 2023
Posts: 2
Likes: 0
same here did you fix it
Pick up my 2017 C7 ZO6 from storage last week and drove it for about 10 miles before the identical issue happen to me the engine began running rough and the service rear axle came on as well as the stabiltrack light came on. When I got home I plugged into he OBD and got the same code PO302 misfire in cylinder 2. I swapped the coils and check the plugs but no signs of any issues and it still is running rough.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,564
Likes: 4,034
From: Cape Coral, Florida
Did you check for any spark on # 2 cylinder before condemning the coil pack ??…they rarely go bad…you also be looking at the coil pack wiring before you change it…a coil pack can be checked to see if it is putting out a spark with a 12 volt test light connected to battery positive probing the “control” wire…the engine doesn’t even have to be running to make it spark.
Melting Slicks
Joined: Feb 2018
Posts: 2,157
Likes: 1,032
From: North Texas
Did you check for any spark on # 2 cylinder before condemning the coil pack ??…they rarely go bad…you also be looking at the coil pack wiring before you change it…a coil pack can be checked to see if it is putting out a spark with a 12 volt test light connected to battery positive probing the “control” wire…the engine doesn’t even have to be running to make it spark.
Could you please explain the how and why of this procedure?
Engine off?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,564
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From: Cape Coral, Florida
This is just a quick functional check of the coil pack also called a “scratch test”….ignition is ON (ACC button held down for 5 seconds) and the coil pack “control” wire is back probed…test light connected to battery positive and then you scratch or tap the back probe with the tip of the test light…each coil pack knows when to fire by the inputs from the crankshaft position sensor.
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Burning Brakes
Joined: Mar 2022
Posts: 1,220
Likes: 733
From: Phoenix, Arizona
"This is just a quick functional check of the coil pack also called a “scratch test”….ignition is ON (ACC button held down for 5 seconds) and the coil pack “control” wire is back probed…test light connected to battery positive and then you scratch or tap the back probe with the tip of the test light…each coil pack knows when to fire by the inputs from the crankshaft position sensor."
Just to clarify @C5 Diag , "back probed" would just be a metal probe (conductor not connected to anything) inserted into the control wire correct? And if you don't have a wiring schematic you could insert the probe into either of the connector wires and try the scratch test? If you have the wrong wire, simply no spark but the correct wire should result in a spark. If none spark safe to assume bad coil?
Just to clarify @C5 Diag , "back probed" would just be a metal probe (conductor not connected to anything) inserted into the control wire correct? And if you don't have a wiring schematic you could insert the probe into either of the connector wires and try the scratch test? If you have the wrong wire, simply no spark but the correct wire should result in a spark. If none spark safe to assume bad coil?
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,564
Likes: 4,034
From: Cape Coral, Florida
"This is just a quick functional check of the coil pack also called a “scratch test”….ignition is ON (ACC button held down for 5 seconds) and the coil pack “control” wire is back probed…test light connected to battery positive and then you scratch or tap the back probe with the tip of the test light…each coil pack knows when to fire by the inputs from the crankshaft position sensor."
Just to clarify @C5 Diag , "back probed" would just be a metal probe (conductor not connected to anything) inserted into the control wire correct? And if you don't have a wiring schematic you could insert the probe into either of the connector wires and try the scratch test? If you have the wrong wire, simply no spark but the correct wire should result in a spark. If none spark safe to assume bad coil?
Just to clarify @C5 Diag , "back probed" would just be a metal probe (conductor not connected to anything) inserted into the control wire correct? And if you don't have a wiring schematic you could insert the probe into either of the connector wires and try the scratch test? If you have the wrong wire, simply no spark but the correct wire should result in a spark. If none spark safe to assume bad coil?
Yes, here is a picture of a back probe (4mm jack), a piercing probe and a T pin…best to backprobe a wire connector vs front probe where you might possibly spread the terminal apart…you can buy back probes on Amazon for cheap…if you have a DVOM get yourself new leads with 4mm banana jacks so you can plug the leads into the back probes…if you are checking a Corvette 4 wire coil pack 1 wire is power, 1 is ref ground, 1 is a block ground and 1 is the “control wire”…if you don’t have any info for your car I highly suggest you get a subscription to Alldata…you can get a sub for 1 month, 1 year, or 3 years…it has EXCELLENT service info in there….other ignition systems wiring is different for different cars…you have to know their design…a lot of good info on YouTube !!
Last edited by C5 Diag; Jun 16, 2023 at 12:19 PM.
Burning Brakes
Joined: Mar 2022
Posts: 1,220
Likes: 733
From: Phoenix, Arizona
Thank you for clarifying all of that, I know it helps me and so many others. And I fully echo your endorsement of Alldata, my annual subscription has paid for itself many times over.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,564
Likes: 4,034
From: Cape Coral, Florida
I’ve used Mitchell too but Alldata is MUCH better…there are some wiring discrepancies I’ve noticed in Alldata on some ground circuits.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,564
Likes: 4,034
From: Cape Coral, Florida
Here’s a short video below on that test…I’ve wrenched long enough in my aviation career…auto diagnostics is more challenging and easier on the body…makes you use your noggin !!
Last edited by C5 Diag; Jun 17, 2023 at 09:53 AM.
Melting Slicks
Joined: May 2002
Posts: 2,474
Likes: 756
From: Laporte, IN
Found that happened to me and also a friend. After sitting over the winter with a few short startups in the storage time. Upon taking it out from storage in the spring same misfire issue. My thoughts are the these spark plug do not like short engine runs without getting to normal operating temp. We replace ether all or the miss firing plugs and now everything is normal. So anytime I start the engine over winter will run engine till it is at or close to normal operating temp.
Melting Slicks
Joined: Feb 2018
Posts: 2,157
Likes: 1,032
From: North Texas
But I had all the A&P's do all the hard stuff for me like R&R.
I mainly worked on the radar bench.
Heel & Toe
Joined: Dec 2020
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From: Oregon