2008 BMW P0304: What It Means & Is It Safe to Drive?
P0304 on the 2008 BMW: Cylinder 4 Misfire Detected. Here's what it means, what usually causes it, what repairs typically cost, and whether it's safe to keep driving.
PowertrainHigh urgency
What this code means
Misfire confirmed on cylinder 4. On 4-cylinder engines, this is the last cylinder—check coil and plug first, then injector, then compression.
Common causes on the 2008 BMW
- Worn spark plug on cylinder 4
- Failed ignition coil on cylinder 4
- Faulty or clogged fuel injector
- Low compression or valve issue
Symptoms
- Check Engine Light
- Rough idle and shaking
- Poor acceleration or power loss
Typical fixes
- Replace spark plug and COP coil on cylinder 4
- Clean or replace fuel injector
- Compression and leak-down test if basic parts check out
Repair cost range
For a 2008 BMW, repairs for P0304 typically fall between $150 and $900, depending on the root cause and labor rates in your area.
Known issues on BMW
BMW N54 P0304 on cylinder 4 often indicates a high-pressure injector failure—rear injectors run hotter and tend to fail first. A cylinder contribution test with ISTA isolates injector vs. coil before any parts are ordered.
Most commonly affected models
335i N54 2007–2013535i N55 2011–2016X5 N54 2008–2010