[kajyy]

I have a 2023 2ss FBO e85. I recently had an exhaust leak at the header on the driver side so I had to replace it. After the new header was installed, the car jerks very slightly at idle and very low rpm and hearing popping noise come from exhaust. Chevy mechanic stated that it has misfires in 3, 5, and 7 but not enough for code to pop up and short term fuel trim is a little high (car is running rich)

I am tuned from GPI and they told me only way to fix the fuel trim issue is to fix the misfire first so, i bought new plugs (LTR 7IX-11) and changed the wires and coils and still having the same issues.

Does anyone know what this issue could possibly be, mind you im only at 5k miles on the car?!?

[RIPws6]

It might be caused by a vacuum leak after the header replacement which can cause lean misfires, prompting the ECU to add fuel. E85’s higher fuel volume requirements will amplify it. Common spots to check are the intake manifold gaskets, throttle body, or check the PCV system.

[bishopts]

Do you have cats? Clogged bank 1 cat could cause rich conditions and blow the exhaust gasket out.

[FlukeSS]

Originally Posted by kajyy

I have a 2023 2ss FBO e85. I recently had an exhaust leak at the header on the driver side so I had to replace it. After the new header was installed, the car jerks very slightly at idle and very low rpm and hearing popping noise come from exhaust. Chevy mechanic stated that it has misfires in 3, 5, and 7 but not enough for code to pop up and short term fuel trim is a little high (car is running rich)

I am tuned from GPI and they told me only way to fix the fuel trim issue is to fix the misfire first so, i bought new plugs (LTR 7IX-11) and changed the wires and coils and still having the same issues.

Does anyone know what this issue could possibly be, mind you im only at 5k miles on the car?!?

Do you have a cam? LTR7's are not normally used unless you cam or supercharge the car. Those sparkplugs you replaced, if they are not gapped properly they will cause misfires after the fact.

Ask me how I know... my car uses .025 gap not the stock .040. And yes, I had bank 1 misfires as well. In my case blown spark plugs, then not properly gapped after new ones were installed. I checked everything on the list below except the Fuel System and Fuel Rail Pressure sensor, then went back to the spark plugs when I figured the gaps were wrong.



Also there are a laundry list of things that can cause misfires.

1. Spark Plugs - Replaced 4 times - Gap not set properly after replacing
2. Plugwires - Replaced 2 times.
3. Vacuum Leak - Tested no leak
4. Injectors - No issue found
5. Injector Coils - No issue found
6. Fuel System/rail/pump - Did not check
7. O2 Sensors - Replaced upstream left/right O2 sensors
8. MAF sensor - Cleaned
9. Cylinder compression loss - Cylinder compression tested - Passed
10. Fuel Rail pressure sensor - Did not check

I'm sure there's more I'm forgetting... but these are the ones I remember off the top of my head that I had to run through.