P0300 Random or Multiple Cylinder Misfire
Caution
The engine is misfiring, and not on just one cylinder. Worn spark plugs and ignition coils are the usual cause, then vacuum leaks and fuel delivery. With a steady light, fix it within days. With a flashing light, slow down and stop driving as soon as it is safe.
- Safe to drive?
- Only gently, and not if the light flashes
- Typical cost at a shop
- $125-$953 RepairPal national averages, parts and labor
- Emissions test
- Yes, while the check engine light is on, most OBD emissions tests fail the car.
- Carmaker bulletins
- 5 notes with links
What it means
The computer watches how fast the crankshaft turns. Each time a cylinder fires, the crank speeds up a little. When a cylinder does not fire, the crank slows where it should speed up, and the computer counts a misfire. P0300 means the misses are spread over several cylinders, or the computer cannot pin them to one. You often feel it as a shake at idle, a stumble or lost power.
The technical version
The misfire monitor runs all the time. It counts misfires over short windows of crankshaft turns. If the rate is high enough to overheat the catalytic converter, the check engine light flashes while the misfire is happening. If the rate is only high enough to raise emissions, the light comes on steady, usually after two drives. Single-cylinder codes are P0301 to P0312. Many cars also store per-cylinder misfire counts in Mode 06.
Official name: Random/Multiple Cylinder Misfire Detected.
Symptoms
- A shaking or rough idle.
- Stumbling, jerking or loss of power when you accelerate.
- A flashing check engine light when the misfire is bad.
- A smell of fuel from the exhaust.
- Worse fuel economy.
Causes, most likely first
| Cause | How likely | How to tell |
|---|---|---|
| Worn spark plugs | most common | They are near or past their service interval. The misfire is worse under load or when you accelerate hard. |
| A weak ignition coil (or old plug wires) | common | One cylinder counts more than the others. Swap that coil to another cylinder: if the misfire moves, the coil is bad. |
| A vacuum leak | common | Misfires mostly at idle, with lean fuel trims and often P0171 or P0174. |
| Low fuel pressure or dirty injectors | less common | Misfires under load on several cylinders, lean trims that get worse with revs. |
| Valve timing or mechanical faults: a stretched timing chain, a worn cam, low compression | rare | Cam or crank correlation codes (P0016), a rattle on a cold start, or a failed compression test. |
| Bad fuel | rare | The misfire started right after a fill-up, on all cylinders. |
How likely is our ranking from repair data and common practice, not a published rate.
What the live data shows
Misfire counts per cylinder are the best clue, where the car reports them. Counts spread over all cylinders point to something they share: plugs due as a set, fuel pressure, a vacuum leak, bad fuel. One or two cylinders far ahead of the rest point to their own plug, coil or injector. Fuel trims tell you whether the mixture is lean, and the freeze frame shows the rpm and load when the code set.
We do not have a recorded drive with P0300 yet, so there is no chart here. What we can show is a healthy baseline: on our own 2010 Honda Accord, the Mode 06 misfire counts from the last drive read 0 on cylinders 2, 3 and 4 on every scan from August 14 to September 24, 2026, and 0 to 3 on cylinder 1. With a real P0300, those counts climb well above that on several cylinders, rpm dips at idle, and short-term fuel trim jumps around because unburned oxygen reaches the front sensor.
What to check first, in order
-
Is the light flashing? If yes, slow down, avoid hard acceleration and stop driving soon.
A flashing light means the misfire is bad enough to overheat the catalytic converter.
What the data shows: Misfire counts rise fast while the light flashes.
Cost: free
-
Read codes, freeze frame and Mode 06 misfire counts.
Other codes (P0171, P0174, P0016) point to the cause. Counts show which cylinders miss.
What the data shows: All cylinders counting: shared cause. One or two cylinders: that cylinder's parts.
Cost: no cost if you have a scanner
-
Check the spark plugs' age and condition.
Plugs are the most common and cheapest fix.
What the data shows: After new plugs, misfire counts should drop to near 0 on the next drive.
Cost: $288-$399 at a shop (Spark plug replacement, RepairPal)
-
Swap coils between cylinders.
If the misfire follows the coil, the coil is bad. This costs nothing.
What the data shows: Watch the per-cylinder counts after the swap.
Cost: $238-$320 at a shop (Ignition coil replacement, RepairPal)
-
Look for vacuum leaks and check fuel trims.
Lean running causes misfires on several cylinders at once.
What the data shows: High positive long-term fuel trim at idle that improves at 2,500 rpm points to a leak.
Cost: free to look
-
Test fuel pressure, then compression.
If spark and air are fine, fuel or mechanical faults are left.
What the data shows: Some cars show fuel rail pressure live. Compression needs a gauge.
Cost: $768-$953 at a shop (Fuel injector replacement, RepairPal)
Is it safe to drive?
Caution
Only gently, and not if the light flashes. Misfires send unburned fuel into the catalytic converter, which can overheat it.
It depends on the light. A steady light with a light stumble: drive gently and get it fixed within days. A flashing light: unburned fuel is overheating the catalytic converter. Slow down, do not tow or climb long grades, and stop driving as soon as it is safe. A misfire left alone often turns into a P0420 and a converter bill.
Stop driving and get help if
- The check engine light flashes.
- The engine shakes hard or loses a lot of power.
- You smell fuel or see smoke.
What it costs
| Repair | Typical cost |
|---|---|
| Check engine light diagnosis (shop)RepairPal, updated September 3, 2026 | $125-$183 |
| Engine compression testRepairPal, updated September 3, 2026 | $216-$317 |
| Ignition coil replacementRepairPal, updated September 3, 2026 | $238-$320 |
| Spark plug replacementRepairPal, updated September 3, 2026 | $288-$399 |
| Fuel injector replacementRepairPal, updated September 3, 2026 | $768-$953 |
National averages for the full job at a shop, parts and labor, from RepairPal (updated September 3, 2026). Your price depends on the car and the area. Many of the first checks on this page cost nothing with a scanner. CarMD found the average check engine repair in 2025 was $554, from more than 39 million US vehicles. Ignition coil and spark plugs together were CarMD's number 3 check engine repair in 2025 ($480), ignition coil alone number 5 ($256), spark plugs alone number 10 ($299). Fuel injectors were number 7, at an average of $572. CarMD averages come from a different method (repairs reported by its users), so they can sit below RepairPal's shop estimates.
Sources for the notes: CarMD 2026 Vehicle Health Index (press release, April 22, 2026).
Can I clear it? Will it come back?
Clear the code after the repair and drive normally. The misfire monitor runs all the time, so a real misfire usually shows up again within one or two drives. Check the per-cylinder counts after the first drive: they should be at or near 0.
Will it fail an emissions test?
Yes, while the check engine light is on, most OBD emissions tests fail the car.
Carmaker notes
Service bulletins and warranty extensions that name this code. Ask a dealer to check your VIN.
-
Honda 2008-2012 Accord V6 automatic
Honda bulletin 13-078 (version 11, December 2018): piston rings on some cylinders can line up and foul the spark plugs, with P0301 to P0304. Coverage is 8 years from purchase with unlimited miles, from a class action settlement.
Honda 13-078 via NHTSA static.nhtsa.gov
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Chrysler, Dodge, Jeep 2011-2013 models with the 3.6L V6 (Journey, 200, Avenger, Challenger, Charger, 300, Grand Caravan, Town and Country, Durango, Grand Cherokee; 2012-2013 Wrangler)
Warranty extension X56 (bulletin 09-002-14 REV. A, October 2014): P0300, P0302, P0304 or P0306 from the left cylinder head. Coverage is 10 years or 150,000 miles from the in-service date.
Chrysler 09-002-14 REV. A via NHTSA static.nhtsa.gov
-
Ford 2014-2019 Fusion and 2017-2019 Escape 1.5L EcoBoost
Ford bulletin 19-2139 (November 2019): P0300 to P0304 and related codes may come from coolant getting into a cylinder. The fix is a new short block and head gasket.
Ford TSB 19-2139 via NHTSA static.nhtsa.gov
-
GM 2014-2016 Silverado, Sierra, Tahoe, Suburban, Yukon, Escalade with 5.3L or 6.2L; Corvette 6.2L
GM bulletin 15-06-01-002B (November 2015): P0300 may come from a collapsed or stuck active fuel management (AFM) lifter.
GM 15-06-01-002B via NHTSA static.nhtsa.gov
-
Honda 2016-2017 Pilot, 2017 Ridgeline, 2018 Odyssey
Honda bulletin 20-100 (February 2021) covers P0300 to P0306 from injector wear, for 10 years or 150,000 miles.
Honda 20-100 via NHTSA static.nhtsa.gov
Related codes
Also related, no guide yet: P0302, P0304, P0305, P0306, P0307, P0308.
How Obie handles P0300
Obie reads the misfire counts per cylinder where the car reports them, the fuel trims and the freeze frame, and tells you whether the pattern points to something all cylinders share or to one cylinder's plug or coil. If the light is flashing, Obie tells you to slow down first. Obie is part of ScanMyCar Pro. Codes and live sensors are free.
Questions people ask
Can I drive with a P0300 code?
With a steady light and a mild stumble, drive gently for a few days until it is fixed. With a flashing light, slow down and stop driving as soon as it is safe.
What is the most common cause of P0300?
Worn spark plugs, then weak ignition coils. Vacuum leaks and fuel delivery come next.
Can a bad catalytic converter cause P0300?
Rarely. It is usually the other way around: misfires damage the converter. A badly clogged converter can cause misfire-like symptoms, but that is not common.
Why do I get P0300 but no single-cylinder code?
The misses are spread over several cylinders, or the computer cannot tell which cylinder missed. Mode 06 misfire counts can still show which cylinders are involved.
Will new spark plugs fix P0300?
Often, if the plugs are old. If the misfire stays after new plugs, swap coils and check for vacuum leaks next.
Sources
- RepairPal: P0300 code page repairpal.com
- RepairPal: Check engine light diagnosis (shop) (updated September 3, 2026) repairpal.com
- RepairPal: Engine compression test (updated September 3, 2026) repairpal.com
- RepairPal: Ignition coil replacement (updated September 3, 2026) repairpal.com
- RepairPal: Spark plug replacement (updated September 3, 2026) repairpal.com
- RepairPal: Fuel injector replacement (updated September 3, 2026) repairpal.com
- CarMD 2026 Vehicle Health Index (press release, April 22, 2026) prnewswire.com
- Honda 13-078 via NHTSA static.nhtsa.gov
- Chrysler 09-002-14 REV. A via NHTSA static.nhtsa.gov
- Ford TSB 19-2139 via NHTSA static.nhtsa.gov
- GM 15-06-01-002B via NHTSA static.nhtsa.gov
- Honda 20-100 via NHTSA static.nhtsa.gov
- Texas DPS emissions testing FAQ dps.texas.gov
- Arizona myazcar.com: OBD and the check engine light myazcar.com
A guide, not a diagnosis. This page describes what P0300 generally means across OBD2 cars. What is actually wrong with your car depends on its live data and its history, and any repair decision deserves a proper diagnosis, whether that is you with a scanner or a professional with a lift.
