C8 Stingray Rough Idle and Acceleration after Headers
Thread Starter
6th Gear
Joined: Apr 2026
Posts: 6
Likes: 1
C8 Stingray Rough Idle and Acceleration after Headers
I installed Race Engineering long tube headers on my C8. Noticed when header is off it does have the possibility to hit the sparks. After installing it, test drive showed a pretty severe idle and acceleration had a lot of backfire in full throttle. P0300 code popped up and flashing engine light.
checked the spark plugs since I knew they could touch the header during install and cylinder 7 had a cracked plug. Changed it. Car ran a lot better after, no codes. Slightly rough idle and acceleration was perfect until the next day when it started backfiring again full throttle around 4,500RPMs. Idle is still loads better than when the plug was cracked and all other plugs seemed.. ok, car has 20,000 miles.
should I replace all plugs? Coil wires too? Everything else seemed fine, just not sure.
vacuum lines are good, header gaskets were put on straight.
checked the spark plugs since I knew they could touch the header during install and cylinder 7 had a cracked plug. Changed it. Car ran a lot better after, no codes. Slightly rough idle and acceleration was perfect until the next day when it started backfiring again full throttle around 4,500RPMs. Idle is still loads better than when the plug was cracked and all other plugs seemed.. ok, car has 20,000 miles.
should I replace all plugs? Coil wires too? Everything else seemed fine, just not sure.
vacuum lines are good, header gaskets were put on straight.
Intermediate
Joined: Sep 2025
Posts: 30
Likes: 21
From: Lufkin, Texas
I would change all the plugs and the wires and install hi temp plug wire sleeve's, You might have cooked the plug wires. How do the headers route? Are the headers at all by the plug wires being they go up?
Thread Starter
6th Gear
Joined: Apr 2026
Posts: 6
Likes: 1
in between the headers, about 2 inches away is the spark boots. Wires go down as the coils are underneath. Maybe 10 inches away. Coil wires have heat sleeves on them.
Intermediate
Joined: Sep 2025
Posts: 30
Likes: 21
From: Lufkin, Texas
Start with the easy stuff first and take your time inspecting everything, You already found 1 cracked plug, I would change the rest of them, set the plug gap to spec. and inspect the one's removed real good for cracks and make sure you double check the plug wires and any other electrical connection and vacuum line you removed for the installation, you probably just have something simple wrong that's easy to miss, been there done that.
Thread Starter
6th Gear
Joined: Apr 2026
Posts: 6
Likes: 1
Start with the easy stuff first and take your time inspecting everything, You already found 1 cracked plug, I would change the rest of them, set the plug gap to spec. and inspect the one's removed real good for cracks and make sure you double check the plug wires and any other electrical connection and vacuum line you removed for the installation, you probably just have something simple wrong that's easy to miss, been there done that.
