Cylinder 7 Contribution/Balance

What it means

The engine computer compares the power each cylinder adds, usually by watching crankshaft speed changes after each combustion event, and found that cylinder 7 differs from the others by more than the allowed limit. The most common cause is the cylinder 7 injector not delivering the correct amount of fuel, though low compression in that cylinder can do the same. Cylinder 7 only exists on engines with eight or more cylinders, such as V8 engines.

Related codes: P0307P0207P0300P0171P0172

Symptoms4

• Rough or uneven engine running, especially at idle.
• Loss of power and higher fuel consumption.
• Check engine light on, possibly with the misfire code P0307.
• Black smoke from the exhaust if the injector leaks extra fuel, especially on diesel engines.

Possible causes6

• Dirty or partly clogged cylinder 7 injector delivering too little fuel.
• Leaking or sticking cylinder 7 injector delivering too much fuel.
• Worn injector with excessive return (leak-off) flow on diesel engines.
• Weak ignition in this cylinder from the spark plug or ignition coil on gasoline engines.
• Low compression in cylinder 7 from valve, piston ring or head gasket problems.
• Air leak near this cylinder's intake runner, or an intermittent injector connector.

How to diagnose6

1. Read all codes and watch the cylinder 7 misfire counter on a scan tool.
2. On diesels, view the injector correction or balance values; on gasoline engines, run a cylinder power balance test if the scan tool supports it.
3. On gasoline engines, swap the ignition coil and spark plug with cylinder 8; if the fault moves, the cause is ignition, not the injector.
4. Test the cylinder 7 injector: a flow and leak test on gasoline engines, or a return flow test on diesels.
5. Have a compression or leak-down test done if the injector and ignition check good.
6. Inspect the injector connector, wiring and this cylinder's intake runner for leaks or intermittent contact.

How to fix6

1. Repair the injector connector or any air leak near the intake runner if found.
2. Replace the spark plug or ignition coil if the fault moved with them.
3. Clean the cylinder 7 injector on an injector cleaning machine if it is dirty.
4. Replace the cylinder 7 injector if it leaks or its flow is out of specification, and code it to the computer if the engine requires it.
5. Repair the valves or head gasket if testing confirms low compression.
6. Clear the codes, then road test and confirm the balance values are back to normal.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

The cost is low when injector cleaning or a spark plug fixes it, and rises when the injector must be replaced, especially on diesel and direct-injection engines; internal engine repair is a separate and higher cost.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.
Prices last updated: September 2026

Frequently asked questions