P0301 is more useful than P0300 because your Mustang has named the cylinder. On the 5.0L Coyote V8, cylinder 1 sits at the front of Bank 1 — the passenger-side bank — and its coil and plug are among the easier ones to reach. On the 2.3L EcoBoost, cylinder 1 is at the accessory-drive end of a single inline bank. Either way the same two free tests separate the two most likely causes in about fifteen minutes. The Mustang-specific twist: on a Gen 3 Coyote, an oil-fouled plug from the documented consumption condition can present as a single-cylinder misfire before it becomes a general one.
Match the symptom
Select the closest observation. The result changes the first test; it does not name a part to replace.
Classic single-cylinder misfire. At idle nothing masks the missing contribution. Pull the freeze frame before touching anything — it records the conditions where the misfire actually happened.
Confirming the cylinder 1 repair held
Write down the freeze frame and all cylinder counters before clearing anything. Clearing first destroys the record of conditions you need to reproduce, and on a car whose misfire may only appear at high rpm that record is everything.
Then drive the rpm, load and temperature window the freeze frame recorded and watch the cylinder 1 counter. Zero counts across those exact conditions is the proof. A dark dashboard during a gentle drive proves nothing about a fault that appeared at 6,000 rpm.
If the plug was oily, check it again in a few thousand miles even if the misfire has gone. A plug that is fouling again tells you the oil is still arriving, and that is a different repair from the one you just did.
What can set P0301—and how to separate it
The order below is evidence-driven, not a universal probability ranking. Vehicle year, repair history, companion codes and the operating condition in freeze frame change where diagnosis should begin.
| Possible cause | Evidence that supports it | First useful test |
|---|---|---|
| Failing coil on cylinder 1 | Misfire follows the coil when moved to another cylinder; carbon tracking in the boot | Swap the cylinder 1 coil with a neighbour, clear the code and see whether the misfire moves |
| Worn or fouled spark plug | Cylinder 1 plug differs from the others — eroded electrode, cracked insulator, oil or fuel fouling | Remove it and compare directly against the other plugs and the specification for your engine |
| Oil fouling from consumption (2018–2020 Coyote) | Oil level dropping with no external leak; plug oily rather than merely worn | Check oil level and measure the consumption rate over a known distance |
| Injector fault on cylinder 1 | Misfire stays after plug and coil are eliminated; injector quiet or resistance out of line | Listen with a stethoscope, compare resistance, then run the scan tool's injector test |
| Coolant reaching that cylinder (pre-2020 2.3L) | Coolant loss with no external leak; white smoke; overheating history | Pressure-test the cooling system and run a combustion-gas test |
| Low compression on cylinder 1 | Misfire will not follow any component; relative compression down on that cylinder | Run relative compression from the scan tool, then a mechanical compression or leak-down test |
Where cylinder 1 is, by engine
On the 5.0L Coyote V8, cylinder 1 is at the front of Bank 1, which is the passenger-side bank. That is genuinely convenient — it is one of the more accessible coils and plugs on the engine, so both of the free tests below are quick.
On the 2.3L EcoBoost, there is only one bank. Cylinders run in a line from the accessory-drive end, and cylinder 1 is at that end.
On the 3.7L V6, the layout is different again and worth confirming for your specific car rather than assuming, because carrying over a V8 convention will send you to the wrong side.
The two free tests, in order
First, pull the cylinder 1 plug and lay it beside the others. What you find narrows the cause immediately. A light tan insulator means it was firing correctly and the fault is elsewhere. Wet with fuel means no ignition at all. Sooty black means rich. And oily means oil is entering the chamber — which on a Gen 3 Coyote points at the consumption condition rather than at anything you can fix with a coil.
Second, swap the cylinder 1 coil with a neighbouring one. Label both, clear the code, then drive the conditions your freeze frame recorded. If the code returns naming the cylinder that now holds the original coil, the coil is faulty and you proved it for nothing. If it comes back as P0301, the coil is fine and the most common cause is eliminated.
Between them these two tests cost nothing and resolve most single-cylinder misfires. On a V8 in particular they are worth doing before buying anything, because eight coils is a serious bill for information the code already gave you.
When it is oil rather than ignition
This is the Mustang-specific branch. Ford's 2019 bulletin describes affected 2018–2020 Gen 3 Coyote engines consuming over a quart of oil every 3,000 miles with no visible external leak, associated with internal vacuum during deceleration and with piston ring sealing.
Oil that reaches a combustion chamber fouls the plug in that cylinder, and a fouled plug misfires. So the sequence people run into is: P0301 appears, a new plug fixes it for a while, then it returns — because the oil is still arriving and fouling the new plug too.
If the cylinder 1 plug comes out oily and your oil level has been dropping with nothing on the driveway, stop and measure the consumption rate properly over a known distance. That measurement is also the evidence any bulletin or warranty conversation will require, so it is worth starting early rather than when you need it.
Why replacing all eight is the wrong instinct
- P0301 already named the cylinder — that is the code doing the hard part for you
- Eight coils on a V8 is eight times the cost for no extra information
- It disturbs seven connectors that were working perfectly
- If the cause is oil, an injector or compression, new coils change nothing at all
- The coil swap answers the same question for free in fifteen minutes
Save these scan-data clues
Freeze frame is a snapshot of conditions when the PCM matured the fault. It can distinguish an idle-only problem from a load, cold-start or monitor-completion problem. Clearing first throws that context away.
- Misfire counters for every cylinder, confirming cylinder 1 genuinely dominates
- Engine rpm and load when the counters climbed — idle, high rpm and boost point differently
- Engine coolant temperature, separating a cold-start fault from a heat-related one
- Short and long-term fuel trim; positive trims suggest air or fuel rather than ignition
- Any companion codes — lean codes, knock data or a second misfire code change the order
- Vehicle speed and throttle position at the time of the fault
A practical diagnostic workflow
- 01Check the oil level and condition
On a 2018–2020 Coyote this comes first. Low oil with no external leak, alongside a misfire, points at the documented consumption condition rather than at any ignition component.
- 02Confirm cylinder 1 is genuinely dominating
Read all counters. If several cylinders are climbing together, you have a broader problem than one failed part and the diagnosis changes.
- 03Pull the cylinder 1 plug and read it
Compare it against the others. Oily, wet, sooty or clean each point somewhere different, and on the Coyote cylinder 1 is one of the easier plugs to reach.
- 04Swap the coil and label both
Move the cylinder 1 coil to a neighbouring cylinder, clear the code and drive the freeze-frame conditions. If the misfire follows, you have found it without spending anything.
- 05Inspect the boot and connector
Carbon tracking looks like a thin black line down the insulator and lets spark escape to ground. A broken connector lock lets the coil work loose under vibration — more likely on a car driven hard.
- 06Declare and remove any tune
If the car is modified, returning to stock calibration is a diagnostic step. A tune asking for more timing than the fuel supports produces misfire that no factory tree will find.
- 07Test the injector on that cylinder
With plug and coil eliminated, listen to the injector, compare its resistance with the others, and use the scan tool's injector test where available.
- 08Check compression when nothing moves the fault
Relative compression from the scan tool first, then a mechanical compression or leak-down test. This is where the job stops being a weekend task.
Do not replace all eight coils because one cylinder misfired — that is eight times the cost for information P0301 already gave you free. Pull the plug, then swap the coil. And if that plug comes out oily on a 2018–2020 Coyote, stop: you are looking at the documented oil-consumption condition, and no ignition part will fix a plug that keeps getting fouled.
Ford service bulletins that name P0301
A bulletin does not automatically apply to your truck. Check the exact model year, engine and build date it covers, and have a dealer or shop confirm whether your VIN is included before paying for the work it describes.
| Bulletin | Applies to | What it says |
|---|---|---|
| Ford TSB (2019) — Gen 3 Coyote oil consumption | Certain 2018–2020 5.0L Coyote engines | Ford advised dealers of excessive oil consumption on affected Gen 3 engines — reportedly over one quart per 3,000 miles with no visible external leak. The condition is associated with strong internal vacuum when fuel injection is reduced during deceleration, and with piston ring sealing. Confirm VIN coverage with a dealer rather than assuming it applies. |
P0301 repair cost comparison
These are planning ranges gathered from public U.S. estimate data, not quotations. Your figure moves with local labour rates, model year, engine and whether the shop bills diagnosis separately. Use them to judge whether a quote is reasonable — not to decide what is wrong.
| Repair | Parts only | Shop total | DIY difficulty | Notes |
|---|---|---|---|---|
| Plug inspection and coil swap | $0 | Part of diagnosis | Easy — 15 minutes on the Coyote | Together these identify most P0301 faults at no cost |
| Single ignition coil | Moderate | Typically under an hour of labour | Easy — coils sit on top on the Coyote | Replace the one you proved faulty, not all eight |
| Spark plug set | Moderate for eight on a V8 | Straightforward access | Easy to moderate | Track-used cars need them sooner than the service interval implies |
| Oil consumption measurement | Cost of oil | Documented test over set mileage | Easy but takes weeks | The evidence any bulletin or warranty conversation will require |
| Injector diagnosis and replacement | Higher on direct-injection engines | Get a quote | Advanced | Only once plug and coil are eliminated by testing |
| Compression or leak-down testing | $0 | Standard diagnostic charge | Moderate with a gauge | Where the misfire refuses to follow any component |
Why the model year changes the test
Two things separate a Mustang from the same engine in a truck. It gets used harder — sustained high rpm, track days and a much higher proportion of modified cars — so heat, oil and fuelling all sit closer to their limits. And two documented faults sit behind a large share of its codes: Gen 3 Coyote oil consumption on 2018–2020 cars, and the 2.3L EcoBoost open-deck head-gasket flaw that Ford redesigned for the 2020 model year. Identify your engine and generation before you read any further.
- On the 5.0L Coyote V8, cylinder 1 is at the front of Bank 1, the passenger-side bank, and is among the more accessible coils and plugs on the engine.
- On the 2.3L EcoBoost there is a single bank, with cylinder 1 at the accessory-drive end.
- 2018–2020 Gen 3 Coyote engines are covered by a Ford bulletin describing oil consumption over a quart per 3,000 miles with no external leak, which fouls plugs and causes misfire.
- Pre-2020 2.3L EcoBoost engines have a documented open-deck head-gasket flaw that lets coolant reach the cylinders. Ford redesigned it for 2020.
P0301 FAQ
Where is cylinder 1 on a Mustang GT?+
At the front of Bank 1 on the 5.0L Coyote, which is the passenger-side bank. It is one of the more accessible cylinders for plug and coil work.
Can I drive with P0301?+
Briefly and gently if the light is steady, and not at all if it is flashing. Track use is out entirely until it is diagnosed.
Why is my cylinder 1 plug oily?+
Oil is reaching that combustion chamber. On a 2018–2020 Coyote that matches the documented consumption condition, and it explains a misfire that keeps coming back after new plugs.
Should I replace the coil or the plug first?+
Inspect the plug first — it costs nothing and frequently shows the fault outright. Then swap the coil to another cylinder. Those two free steps identify most P0301 faults.
Does my aftermarket tune affect this?+
It can cause it. A calibration requesting more timing or boost than the fuel and hardware support produces misfire the factory diagnostic tree cannot explain. Return to stock to find out.
Why did P0301 return after new plugs and coils?+
Because the fault was never in the ignition system. On a Coyote, oil fouling the new plug is a common explanation. Otherwise look at the injector or compression.
Is one misfiring cylinder worse on the 2.3L?+
It feels worse — losing one of four cylinders removes a quarter of the engine, against one of eight on the V8. The diagnosis is the same, but the symptom is far more obvious.
How much does it cost to fix P0301 on a Mustang?+
Usually modest — a plug or a single coil, both accessible on these engines. It becomes expensive when the cause is oil consumption, an injector or compression, which is why the free tests come first.
Ford diagnostic references
These documents explain Ford monitor operation. Exact pinpoint tests, connector views and specifications must be selected for the truck's VIN and model year in current service information.
01Ford 2017 gasoline OBD operation summaryFord EVAP, misfire, fuel and comprehensive-component monitor descriptions↗02Ford 2024–2025 gasoline OBD operation summaryFord monitor logic, enabling conditions and drive-cycle requirements↗03Common problems with the Ford 5.0 Coyote engineCovers oil consumption, the tick, and head-gasket failure by Coyote generation↗04The Coyote engine tick, and why Ford says it is normalExplains Ford's Special Service Message position on the direct-injection ticking noise↗05Ford owner manuals and warranty guidesOfficial year- and VIN-specific manual lookup for your vehicle↗