What does code P0304 mean on a BMW and is it safe to drive?
P0304: Cylinder 4 Misfire Detected. Here's what it means on your BMW, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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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 for your 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 BMW, repairs for P0304 often fall between $150 and $900, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.
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