What does code P0304 mean on a Pontiac and is it safe to drive?
P0304: Cylinder 4 Misfire Detected. Here's what it means on your Pontiac, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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 Pontiac
- 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 Pontiac, 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 Pontiac
Pontiac Ecotec 2.4L P0304 on cylinder 4 is a known timing chain stretch symptom on this engine. Listen for a rattle at cold startup—if present, the timing chain is the root cause rather than a coil or plug failure. The 2.4L Ecotec timing chain stretch is a widely documented issue.
Most commonly affected models