Ignition and misfires code
P0307: Cylinder 7 misfire
How much to fix P0307? Typically $70–$320.
Wide range: this job varies a lot. Itemize your quote for a better answer.
How this range is built
| Part of the job | Low | High |
|---|---|---|
| Parts | $30 | $120 |
| Labor: 0.4 to 1.2 hours × $110 to $150 an hour | $44 | $180 |
| Fees: shop supplies, disposal, diagnostics | $0 | $15 |
| Total, rounded | $70 | $320 |
The hourly rate is the BLS Occupational Employment and Wage Statistics, May 2025 average pay for this trade in the US, $27.13 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 7 is the one skipping its burn. The computer saw weak speed bumps in the crankshaft that line up with cylinder 7's turn. This code only exists on engines with at least seven cylinders, so it applies to V8 engines. A spark, fuel or compression problem is behind it.
- Safe to drive?
- Short trips only
- Most common cause
- Worn spark plug
Steady light: drive gently to a shop. Flashing light: stop to protect the catalytic converter.
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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 or vacuum leak
Check this first
Find cylinder 7 on your V8, then swap its coil with a neighbor on the same bank and clear the code. If the miss moves, replace the coil. If it stays on cylinder 7, check the plug and injector next.
Other repairs that sometimes fix P0307
| Repair | Typical range, US |
|---|---|
| Spark plug replacement | $85 to $510 |
| Fuel injector replacement (one injector) | $170 to $820 |
| Diagnostic scan (check engine light) | $55 to $250 |
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. Many states 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).
P0307 questions
Where is cylinder 7?
On a V8, it is on one bank toward the rear in most layouts, but the numbering differs between makes. Shops use the service manual or a scan tool to confirm which coil goes with cylinder 7.
Plugs or coil?
Test the coil first with a swap, then look at the plug. The coil is usually the quicker test, and plugs are cheap to replace, so doing both on an older engine is common.
Is it serious?
It is not if fixed soon, but repeated misfires can ruin the catalytic converter, which is a far larger bill. If the light flashes, reduce load and get it checked as soon as you can.
How much does it cost to fix P0307?
The most common fix, ignition coil replacement (one coil), has a typical range of $70 to $320 across the US. It is an estimate built from parts prices and local labor wages, not a quote. Your car and shop change it.
Typical range in 10 metro areas
Only the labor rate changes between cities. Same parts, same hours.
| Area | Typical range, estimate |
|---|---|
| Boston area, Massachusetts | $80 to $350 |
| New York City area | $75 to $340 |
| Los Angeles area, California | $75 to $340 |
| Chicago area, Illinois | $75 to $330 |
| Houston area, Texas | $70 to $310 |
| Dallas-Fort Worth area, Texas | $70 to $310 |
| Phoenix area, Arizona | $70 to $320 |
| Atlanta area, Georgia | $75 to $330 |
| Miami area, Florida | $70 to $320 |
| Seattle area, Washington | $80 to $340 |
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.