Repair Cost Estimate
P0304 Repair Cost: Cylinder 4 Misfire Detected
P0304 usually lands in the $120-$1830 planning range after diagnosis. For this estimate, the important cost driver is whether spark plugs, ignition coil, or a deeper ignition and misfire fault is confirmed.
Cost Breakdown
| Line item | Typical cost | Notes |
|---|---|---|
| Diagnostic time | $95-$180 | Often one hour, more if intermittent. |
| Common parts | $35-$1650 | spark plugs, ignition coil, coil boot, fuel injector, compression test |
| Labor after diagnosis | $60-$824 | Access and rust can change labor. |
Why P0304 Estimates Vary
The spread between $120 and $1830 usually comes from access, diagnostic time, and whether the first failed test points to spark plugs, ignition coil, or a deeper system fault. Two vehicles can show P0304 with the same title and still need different labor because engine layout, rust, mileage, and previous repairs change the work.
A written estimate for P0304 should explain what has already been tested. If the quote jumps straight to the most expensive part without power, ground, leak, pressure, or live-data checks, ask for the diagnostic reason before approving it.
Low-End Estimate Usually Means
- The fault was easy to reproduce.
- The failed part or leak was visible and accessible.
- No related codes pointed to a larger upstream issue.
High-End Estimate Usually Means
- Testing was intermittent or required a longer road test.
- The repair involved exhaust, transmission, module, or buried wiring work.
- Related codes had to be diagnosed before P0304 could be verified.
P0304 Estimate Scenarios
The most affordable P0304 repair often comes from finding a small cause before it damages a larger part in the same system. In that situation, the diagnostic charge may be the largest line item because the actual correction can be a hose, connector, cleaning step, gasket, or accessible sensor. The low end still depends on confirming the condition rather than guessing from the code title.
The expensive version of P0304 is an intermittent fault, a buried harness issue, an exhaust or transmission repair, or a condition that needs several drive cycles before it repeats. The high end should include more detail, not less. Ask the shop to separate diagnostic labor, parts, installation labor, programming or calibration if needed, taxes, disposal fees, and a final road-test or readiness-monitor check.
Questions Before Approving P0304 Work
- Which freeze-frame value made the technician focus on ignition and misfire?
- Which test proved spark plugs or the related circuit failed?
- Could P0302, P0303, P0305, P0306 change the order of diagnosis?
- Will the estimate include a post-repair scan and road test?
How to Compare Quotes
Compare P0304 quotes by scope, not only price. One quote may include diagnosis, OEM-level testing, and verification; another may include only a part replacement. The cheaper quote is not cheaper if it skips the test that prevents a second visit.
If you are deciding between DIY and a shop, use the full P0304 code guide to confirm safety, related symptoms, likely causes, and the checks that are reasonable outside a professional bay.
After the P0304 Repair
Do not judge the repair only by whether the warning light is off immediately after clearing codes. The vehicle needs a drive condition close to the original freeze frame, and some monitors need warm-up, cruise, deceleration, idle, or fuel-level conditions before they complete. A good final invoice should state that P0304 did not return after verification and should list any monitors that still need normal driving.
If P0304 is part of an emissions, transmission, fuel, ignition, or sensor fault pattern, ask whether a readiness monitor, adaptive value, relearn, or second road test is needed. Some repairs look complete until the vehicle repeats the original operating condition. Keeping the first scan report, the estimate, and the final verification note gives you a clean record if P0304 returns later or if another related code appears.
P0304 Budget Notes
Use the $120-$1830 range for cylinder 4 misfire detected as a planning band, then adjust for vehicle age, access, rust, diagnostic complexity, and local labor rate. A clean ignition and misfire repair near the low end normally has a repeatable fault and a confirmed cause. A repair near the high end should include a clear reason, such as buried wiring, exhaust work, transmission testing, module communication, or a fault that only appears after a long road test.
Before comparing prices, ask whether the estimate includes the same scope. One shop may quote only spark plugs; another may include testing around ignition coil, scan data, installation labor, and verification. For cylinder 4 misfire detected, the better quote is the one that explains the cause and proves the result, not simply the one with the lowest first number.
DIY or Shop?
DIY is reasonable for P0304 when the inspection is visible and the part is reachable. Use a shop when the job requires smoke testing, scope testing, transmission pressure checks, module programming, or exhaust work under the vehicle.
Avoid Paying Twice
For P0304, do not replace the most expensive part first. Confirm worn spark plugs, failing ignition coil, power, ground, signal, leaks, and related codes before authorizing a repair.
Full P0304 Guide
For symptoms, causes, safety notes, and related codes, read the full P0304 code guide.