P0307 Code: Cylinder 7 Misfire Detected
Cylinder 7 is misfiring. On GM and Hemi V8s it's a cylinder-deactivation cylinder, so check the lifter.
At a glance
Severity: Moderate
- Meaning
- Cylinder 7 Misfire Detected
- System
- Ignition & Misfire · Powertrain
- Safe to drive?
- With caution
- Typical repair cost
- $80–$5,000
- DIY difficulty
- Moderate
P0307 means the engine computer keeps counting missed power strokes on cylinder 7, which only exists on V8, V10 and larger engines. On GM small-blocks and the Chrysler Hemi it is the last cylinder on the driver's side, next to the firewall, and it is one of the four cylinders the engine shuts down to save fuel. That makes P0307 on those trucks different from most misfire codes: a deactivating lifter that sticks or collapses, an oil-control solenoid that won't switch it back on, or oil fouling from cylinder-deactivation oil consumption are all realistic causes next to the usual coil and plug. On Ford V8s cylinder 7 is third from the front on the driver's side, and there the plug itself is the most common problem, especially the two-piece plugs of the 5.4L 3-valve.
Can I keep driving? Drive gently and only as far as the shop while the light is steady. A flashing light means stop, because the catalytic converter is overheating. A loud tick from the driver's side of a GM or Hemi V8 means a lifter may be failing, and running it can wipe out the cam lobe.
How to read P0307
- P Powertrain
- 0 Generic (SAE)
- 3 Ignition / misfire
- 07 Specific fault
Symptoms
- Shudder when the engine switches back from four to eight cylinders at light throttle
- Tick or tap from the rear driver's side of the engine, loudest at idle
- Oil consumption and a wet, black plug on cylinder 7
- Check-engine light flashing during highway merges or towing
- Burnt smell from a plug wire boot touching the exhaust manifold (GM trucks)
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- Collapsed or sticking cylinder-deactivation lifter, or a worn cam lobe on cylinder 7 (GM AFM/DFM, Hemi MDS)
- Worn or oil-fouled plug 7, including oil consumption on deactivated cylinders
- Failed coil 7, or on GM trucks a plug wire boot burned by the exhaust manifold
- Faulty deactivation oil-control solenoid in the lifter oil manifold keeping cylinder 7 switched off
- Clogged or leaking cylinder 7 injector
- Low compression from a burned valve or stuck rings
- Chafed coil or injector wiring at the rear of the driver's-side harness
Diagnosis step by step
Check when the misfire happens
With a scan tool, watch the cylinder 7 misfire counter together with the cylinder-deactivation status. If misses pile up mainly as the engine leaves four-cylinder mode, the lifter or its oil-control solenoid is the prime suspect rather than the coil.
Tools: OBD-II scanner
Inspect the plug wire and coil on the driver's rear corner
On GM V8s the coils sit on the valve cover with short plug wires. Look at the cylinder 7 boot where it passes the exhaust manifold for melted rubber or a white arcing track. Swap coil 7 with coil 5 on the same bank and see if the misfire moves.
Tools: Flashlight, OBD-II scanner
Read plug 7
Pull it and compare with plug 5. A plug wet with oil or covered in hard black deposits points to oil entering the cylinder, which on cylinder-deactivation engines often accompanies a lifter or ring problem. On the Ford 5.4L 3-valve, follow the factory removal procedure for the two-piece plug so the shell doesn't break off in the head.
Tools: Spark plug socket, Torque wrench
Compare cranking compression with a leak-down test
Measure cranking compression on cylinder 7, then do a leak-down test at top dead center. Low compression but a tight leak-down means the valves seal but one isn't opening, the classic signature of a collapsed lifter or flattened cam lobe. Low compression with heavy leakage points to a valve or rings instead.
Tools: Compression tester
Test the deactivation solenoid
On GM engines the cylinder 7 solenoid sits in the lifter oil manifold under the intake. Check for its own circuit code, measure its resistance against the other three solenoids, and command it with a bidirectional scan tool. Low or dirty oil also makes these solenoids stick, so check oil level and condition first.
Tools: Multimeter, OBD-II scanner
Check injector 7 last
If everything above passes, run an injector cut-out or balance test and compare the rpm drop on cylinder 7 with its neighbors.
Tools: OBD-II scanner
Where the parts are
- 1Ignition coil
- 2Spark plug
- 3Fuel injector
- 4Camshaft sensor
- 5Crankshaft sensor
- 6Engine computer (ECM)
- 7Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace coil 7 and plug wire (GM V8) | Yes | $80–$260 |
| Replace spark plugs, V8 full set | Yes | $180–$600 |
| Remove broken two-piece plug (Ford 5.4L 3-valve) | No | $150–$600 |
| Replace cylinder-deactivation oil-control solenoid or lifter oil manifold | No | $400–$1,000 |
| Replace lifters and camshaft (AFM/MDS V8) | No | $2,200–$5,000 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Chevrolet
On 5.3L and 6.2L V8s with Active Fuel Management or Dynamic Fuel Management, cylinder 7 is a deactivating cylinder. Failed lifters and oil-fouled plugs on these cylinders are well documented. If coil and plug swaps don't move the misfire, test for a lifter before anything else.
Ram
On the 5.7L Hemi, cylinder 7 is shut off by the Multi-Displacement System. A persistent P0307 with the well-known Hemi tick often turns out to be a failed lifter roller and a damaged cam lobe. Both spark plugs on cylinder 7 should be checked, not just one.
Ford
On the 5.4L 3-valve V8 in F-150, Expedition and Navigator, the two-piece spark plugs are known to break during removal. A misfire on cylinder 7 often means the plug is well overdue, so plan the plug job with the correct removal procedure and extraction tool at hand.
Field data
| Chevrolet | 3 | Avalanche, Silverado 1500, Silverado 2500 | |
|---|---|---|---|
| GMC | 3 | Sierra 1500 | |
| Ford | 2 | Expedition, F-350 SUPERCAB |
Source: NHTSA Complaints API (US government open data), analyzed by DTC mention.
Emissions / smog test impact
Will fail
A stored P0307 with the check-engine light on fails an OBD emissions test. After a lifter or cam repair, the misfire and catalyst monitors need several drive cycles before they report ready, so don't retest the same day.
Frequently asked questions
Why does my Silverado or Ram set P0307 and not other cylinders?
Cylinder 7 is one of the four cylinders that shut off in fuel-saving mode on these V8s. Their special lifters work harder than the others and fail more often. That's why a P0307 that ignores coil swaps on these trucks is so often a lifter.
Can I just disable cylinder deactivation to fix P0307?
Disabling it with a tuner can stop further wear on a lifter that is only starting to stick, but it won't fix a lifter that has already collapsed or a cam lobe that is worn. Confirm the mechanical condition first with the compression and leak-down comparison.
Is cylinder 7 easy to get to?
On GM trucks it's at the rear of the driver's side, behind the steering shaft and close to the brake booster, so a swivel socket and long extension help. On Ford V8s it is further forward and easier, but the plug depth and the two-piece design on the 5.4L 3-valve make the job slow.
My cylinder 7 plug is oily. Is the engine burning oil?
Probably, at least on that cylinder. On cylinder-deactivation engines, oil can be drawn past the rings of shut-off cylinders or come from a failing lifter. Check oil consumption between changes and do a leak-down test before replacing just the plug.