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P0307: Cylinder 7 Misfire Detected

Severe

Quick answer

P0307 means the engine computer counted too many misfires on cylinder 7, which only exists on V8 and larger engines. Start with the free coil swap and a look at the plug. On GM trucks with Active Fuel Management and Ram trucks with MDS, cylinder 7 is one of the cylinders that deactivates, and a persistent P0307 with a tick often means a collapsed lifter. A flashing light means stop driving.

What it means

The computer counts a misfire when the crankshaft fails to speed up the way it should on a cylinder’s power stroke. Enough missed pulses from cylinder 7 in a set window and it stores P0307, lights the check engine lamp, and on most modern engines shuts off fuel to that cylinder to spare the catalytic converter. The 7 is the manufacturer’s cylinder number, so this code only appears on engines with at least eight cylinders: V8s, V10s and V12s.

Where cylinder 7 sits depends on the engine family. On a GM small-block it is the rearmost cylinder on the driver’s side, and on a Chrysler Hemi the same. On a Ford modular V8 it is the third cylinder back on the driver’s side, since Ford numbers 5 to 8 down that bank. On the Toyota and Nissan V8s the odd cylinders run down the passenger side, so 7 is the rear cylinder there. On the Ford V10, cylinder 7 is the second from the front on the driver’s side. Confirm with a diagram for your engine before you pull anything.

For most engines the usual misfire logic applies: plug, coil, injector, air, compression, in that order of likelihood and price. Cylinder 7 has one twist that matters on two of the best-selling truck engines in America. On the GM 5.3L and 6.2L with Active Fuel Management and the Chrysler 5.7L Hemi with MDS, the cylinders that shut off under light load are 1, 4, 6 and 7, and their special lifters are the ones that collapse or lose their rollers. A P0307 on one of those trucks that survives a coil swap and comes with a ticking noise is a lifter until proven otherwise.

P0307 symptoms: what you'll notice

  • A rhythmic shake or stumble at idle that you can feel through the seat, worse in gear with the brakes on.
  • A ticking or tapping noise from one side of the engine that arrived with the misfire, the classic sign of a collapsed lifter on cylinder-deactivation engines.
  • A flashing check engine light under load: unburned fuel is overheating the catalytic converter. Ease off and stop when it is safe.
  • Reduced power, worse fuel economy and a raw fuel smell from the exhaust, and on cylinder-deactivation trucks the engine may refuse to enter its fuel-saving mode.
  • Companion codes: P0300 when the cause is shared, P0301, P0304 or P0306 alongside P0307 on deactivation engines when more than one special lifter has failed, or a catalyst code (P0420 or P0430) after the misfire has run for a while.

Common causes

Ordered from most to least likely.

  1. 1.

    Worn, fouled or cracked spark plug in cylinder 7

    Still the most common cause on most V8s. Cylinder 7 is often the hardest plug to reach, so it is the one most likely to have been skipped at the last tune-up.

  2. 2.

    Failing ignition coil or coil boot on cylinder 7

    Coil-on-plug units crack, arc through the boot or die when hot. The swap test proves it for free.

  3. 3.

    Collapsed or failed lifter on a cylinder-deactivation engine

    On GM Active Fuel Management and Chrysler MDS engines, cylinder 7 is one of the deactivating cylinders and its lifter is the design that fails. A misfire that ignores the coil swap, comes with a tick, and shows low or uneven compression is this.

  4. 4.

    Clogged, sticking or leaking fuel injector on cylinder 7

    A restricted injector misfires under load, a leaking one at idle or hot restart. Swap-test it where the layout allows, or run an injector balance test.

  5. 5.

    Intake gasket or vacuum leak at cylinder 7’s runner

    Leans out that cylinder alone. Suspect it when the misfire is worst at idle and disappears with load; plastic intake manifolds and their gaskets are the usual site.

  6. 6.

    Low compression from a valve, ring, cam lobe or head gasket problem

    A burnt exhaust valve, a wiped cam lobe on high-mileage engines, broken rings or a head gasket leak into cylinder 7. Suspect it when spark and fuel test good.

  7. 7.

    Wiring or connector fault at the cylinder 7 coil or injector

    Rear cylinders sit under the cowl where harnesses chafe and connectors corrode. Wiggle-test with the engine running.

How to fix it: diagnosis, step by step

Cheapest and most likely checks first.

  1. 1 Read the codes and the freeze frame, then locate cylinder 7

    Note rpm, load and temperature when P0307 set, and whether P0301, P0304 or P0306 are stored with it: several deactivation cylinders misfiring together on a GM or Hemi truck is a lifter pattern. Find cylinder 7 on a diagram for your engine, and note whether it is a deactivating cylinder on yours.

  2. 2 Listen to the engine

    Before touching anything, listen at idle with the hood up. A tick that keeps time with the engine from the cylinder 7 area, especially one that showed up at the same time as the light, is a strong lifter clue. A stethoscope on the valve cover near cylinder 7 makes it obvious.

  3. 3 Watch the misfire counter in live data

    Idle, 2,000 rpm, then loaded in gear with the brakes on. Counts rising only under load say plug or coil; only at idle say leak or leaking injector; steady everywhere say compression or lifter.

  4. 4 Pull spark plug 7 and read it

    Oily, sooty, blistered or cracked all tell a story; a gap far past spec is an answer on its own. If cylinder 7 was skipped at the last tune-up because it was hard to reach, this is where you find out. Replace the full set if it is due, torqued to spec.

  5. 5 Swap cylinder 7’s coil with a neighbor and clear the codes

    Move the coil and boot to another cylinder and that cylinder’s coil to 7, then drive. If the misfire moves, the coil is the answer. If it stays on 7, the coil is proven good. On a deactivation truck with a tick, a misfire that stays put after the swap has just pointed you at the valvetrain.

  6. 6 Test the injector and check for a leak

    Listen for a steady click at the injector, compare resistance with the others, and swap it if the layout allows. Spray carb cleaner around the cylinder 7 runner and gasket at idle and listen for a change, or smoke the intake.

  7. 7 Compression and leak-down on cylinder 7, and on deactivation engines, inspect the lifter

    Measure compression on 7 against its neighbors; more than about 10 to 15 percent low means valves, rings, gasket or cam. A leak-down test says which. On a GM AFM or Hemi MDS engine, a cylinder 7 that shows low compression or an intermittent reading with a tick is a collapsed lifter; the repair is the lifters (all of them, with the deactivation ones replaced or deleted per the shop’s approach) and often the camshaft it damaged.

Known P0307 patterns by make

Brand-specific failure patterns from the field: find your make before parts-shopping.

Chevrolet / GMC 2007–2014 Silverado, Sierra, Tahoe, Suburban, Yukon, Avalanche with the 5.3L (and 6.0L/6.2L) V8 and Active Fuel Management

Cylinder 7 is the rearmost cylinder on the driver’s side and one of the four AFM cylinders (1, 4, 6, 7), and it is the single most common site of the 5.3L’s collapsed-lifter failure. The pattern is P0307, sometimes with P0300, a new tick from the driver’s side, and a misfire that does not move with the coil. The repair is a full set of lifters, often the camshaft, and many shops delete AFM at the same time; a failing lifter that keeps running wipes the cam and raises the bill.

Ram / Dodge / Chrysler / Jeep 2009 and newer Ram 1500, Charger, Challenger, 300, Durango and Grand Cherokee with the 5.7L Hemi and MDS

Cylinder 7 is the rear cylinder on the driver’s side and one of the MDS deactivation cylinders (1, 4, 6, 7). The widely reported Hemi lifter failure, where the roller’s needle bearings let go and the lifter chews the cam lobe, shows up as a tick that grows into a misfire on one of those cylinders. A P0307 with the Hemi tick means pull the valve cover and inspect the lifters and cam before buying ignition parts.

Ford / Lincoln 2004–2010 F-150, Expedition, Navigator and Mustang GT with the 5.4L and 4.6L 3-valve V8

Cylinder 7 is the third cylinder back on the driver’s side, tucked under the cowl on the trucks. The 3-valve’s usual suspects are the coil-on-plug and the two-piece spark plug that seizes and breaks on removal; follow Ford’s penetrating-oil procedure and budget for an extractor. No cylinder deactivation here, so a lone P0307 is almost always ignition; a misfire with a startup rattle points at the cam phasers instead.

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Related codes

Frequently asked questions

What does code P0307 mean?
P0307 means the engine computer has detected repeated misfires on cylinder 7. The code only exists on engines with eight or more cylinders. It is serious: a steady light means fix it soon, a flashing light means raw fuel is overheating the catalytic converter and you should stop driving.
Can I drive with P0307?
With a steady light, short and gentle trips are usually fine. With a flashing light, no. On GM and Ram trucks with cylinder deactivation, a P0307 that comes with a ticking noise deserves a quick diagnosis: a collapsed lifter that keeps running can wipe the camshaft and turn a lifter job into a cam job.
Where is cylinder 7 on my engine?
GM small-block V8 and Chrysler Hemi: the rearmost cylinder on the driver’s side. Ford modular V8: the third cylinder back on the driver’s side. Toyota and Nissan V8: the rear cylinder on the passenger side. Ford 6.8L V10: second from the front on the driver’s side. Always confirm with a diagram for your exact engine.
Why does P0307 point at lifters on GM and Ram trucks?
Because on the 5.3L and 6.2L with Active Fuel Management and the 5.7L Hemi with MDS, the cylinders that shut off under light load are 1, 4, 6 and 7, and the special lifters on those cylinders are the ones that collapse or lose their rollers. A P0307 that survives a coil swap and comes with a tick is that failure more often than not. Cylinder 7 is the most frequently reported of the four on the GM engines.
How do I know if it is the plug or the coil?
Swap cylinder 7’s coil with a neighbor and clear the codes. If the misfire follows the coil, replace the coil. If it stays on cylinder 7, the coil is fine and you look at the plug, the injector, and on deactivation engines, the lifter.
How much does it cost to fix P0307?
A spark plug is $5 to $25; a full set installed on a V8 is $150 to $400. A coil is $40 to $120, $100 to $250 installed. An injector is $100 to $350 installed. A lifter job on a GM AFM or Hemi MDS engine is $1,500 to $3,000 for lifters, and $2,500 to $4,500 when the camshaft has to be replaced too; a deactivation delete adds parts and tuning cost. Most P0307 cases on ordinary V8s end at the plug or the coil.
What is the difference between P0300 and P0307?
P0300 is a random or multiple misfire: the computer sees misses spread across cylinders, which points at something shared, like fuel pressure, a big vacuum leak or timing. P0307 is a misfire counted on cylinder 7 specifically, which points at that cylinder’s plug, coil, injector, runner, valves or lifter. Both together usually mean cylinder 7 is the worst of several.
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