P03E4
Cylinder 8 Combustion Performance
Generic OBD-II
Common symptoms
What you'll notice
- Check spark plugs and replace if necessary
- Inspect ignition coils and replace if faulty
- Clean or replace fuel injectors
- Perform a compression test and check for any issues with the cylinder
- Verify proper air
- fuel mixture and adjust if needed
Common causes
Most likely first
- Faulty spark plug or ignition coil in cylinder 8
- Fuel injector in cylinder 8 is clogged or malfunctioning
- Low compression in cylinder 8 due to worn piston rings or damaged valves
- Vacuum leak in the intake manifold affecting cylinder 8
- Faulty oxygen sensor or air/fuel mixture imbalance in cylinder 8
How to diagnose & fix
Work through it in order
- Engine misfires or runs rough
- Decreased engine power or acceleration
- Excessive exhaust smoke
- Engine stalling or hesitation
- Increased fuel consumption
Read & clear P03E4 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.