Ignition and misfires code
P0308: Cylinder 8 misfire
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $30 | $120 |
| Labor: 0.4 to 1.2 hours × $125 to $175 an hour | $50 | $210 |
| Fees: shop supplies, disposal, diagnostics | $0 | $15 |
| Total, rounded | $80 | $350 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in Boston, $31.54 an hour, times 4 to 5.5 to cover what a shop bills (overhead, tools, insurance, profit). Parts are a band from budget aftermarket to the manufacturer part. Full method.
Not a repair shop, estimates only. Typical range, estimate. Not a quote. Your car, parts and shop change the number.
This is the range for the most common fix, ignition coil replacement (one coil). Which repair your car needs depends on a proper diagnosis.
Cylinder 8 is not firing properly. The computer noticed it by watching the crankshaft slow slightly when cylinder 8's turn comes up. Because it is the last cylinder on a V8, this code does not apply to smaller engines. A weak spark, poor fuel delivery or low compression could be behind it.
- Safe to drive?
- Short trips only
- Most common cause
- Worn spark plug
Steady light: gentle driving. Flashing: stop.
What you may notice
- Rough idle
- Shaking
- Power loss
- Check-engine light
Common causes, most likely first
- Worn spark plug
- Failed ignition coil
- Bad fuel injector
- Low compression
Check this first
Swap the cylinder 8 coil with a neighbor on the same bank and clear the code. If the misfire follows the coil, replace it. If it stays at cylinder 8, test the plug, then the injector, before thinking about compression.
Other repairs that sometimes fix P0308
| Repair | Typical range, Boston |
|---|---|
| Spark plug replacement | $95 to $580 |
| Fuel injector replacement (one injector) | $180 to $910 |
| Diagnostic scan (check engine light) | $60 to $290 |
Before you pay
- Ask the shop what test showed this part is the cause, not just that the code appeared.
- Ask for parts and labor listed separately, and for the hours.
- Ask for a written OK before any extra work. Massachusetts rules require written authorization before repairs.
Got a quote already? Check it against the range. Want to see if your car has a recall tied to this problem? Check recalls by VIN.
Need to read a code yourself? OBD-II scanners on eBay (affiliate link, disclosure).
P0308 questions
What is cylinder 8?
It is the last cylinder in the numbering on a V8. Where it sits depends on the make, but it is on one of the two banks at the rear, so the engine layout diagram settles it.
Is a compression test needed?
If spark and fuel both check out, yes. A compression test tells whether the valves and rings are sealing, and it points to bigger problems, so shops try the cheaper checks first.
Is it expensive?
A coil is typically the lowest-cost fix, and plugs are close behind. The expensive causes are rare, so do not assume the worst. Testing in order keeps the bill reasonable.
How much does it cost to fix P0308?
The most common fix, ignition coil replacement (one coil), has a typical range of $80 to $350 in Boston. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Related codes
More ignition and misfires codes
Code meaning written in our own words. Some codes mean different things on different makes, so check your scan tool or manual. Not a repair shop, estimates only.