P0284: Cylinder 8 is not contributing as much power as the other cylinders
Cylinder 8 contribution/balance fault
Severity: Severity not verified — if the car runs badly, have it inspected
No source in this file rates how urgent a cylinder balance fault is, so the class is not verified. The code means one cylinder is weak, which can come from a failing injector or from engine wear.
It gets more serious if:
- Inspect soon: Inspect soon if the engine misfires, runs rough, loses power or stalls. TroubleCodes.net says a severe imbalance can show up as a rough idle or cylinder misfire.
P0284 in short
P0284 means the engine computer sees cylinder 8 adding less power to the crankshaft than the others. A dirty or failing fuel injector is the most common cause, with mechanical wear such as a leaking valve or head gasket next. Rough running or misfire means get it checked soon.
The computer watches how much each cylinder speeds up the crankshaft during its power stroke. When cylinder 8 adds noticeably less than its neighbours, it sets P0284. It is a comparison between cylinders, not a measurement of the fuel itself.
The usual reason is a fuel injector that is dirty, clogged or failing. Wear inside the cylinder, such as a burnt valve, tired piston rings or a leaking head gasket, can cause the same weak cylinder, so a compression and leakdown check separates a fuel fault from an engine fault.
If an injector was replaced recently, some engines need a learn procedure afterwards, and skipping it can leave a balance code behind.
Most likely causes
These are general causes for this code across vehicles. None is specific to one make or model.
Cause 1: Dirty or failing fuel injector on cylinder 8
Common general cause- Why it ranks here
- TroubleCodes.net lists dirty injectors as the most frequent cause of a cylinder balance fault.
- What would change this
- Rises if injector waveform or sound differs from its neighbours, or a misfire code for the same cylinder is stored. Falls if the injector tests the same as the others.
Cause 2: Mechanical wear in cylinder 8 (valves, rings, head gasket)
Common general cause- Why it ranks here
- The reference list names burnt valves, worn rings and head gasket leaks as the other common causes of one weak cylinder.
- What would change this
- Rises if compression or leakdown for the cylinder is more than about 10 percent off the others. Falls if both are even.
Cause 3: Injector learn procedure not done after an injector replacement
Possible — needs testing- Why it ranks here
- TroubleCodes.net says some vehicles set the code when injectors were replaced without the required learning procedure. It applies only after injector work.
- What would change this
- Rises if the code appeared right after injector work. Falls if no injector has been replaced.
What to test first
Start at step 1. Each result tells you what it means and where to go next.
Step 1: Read all stored codes and freeze-frame data. Note whether a misfire code for the same cylinder is stored with it.
IfA misfire code for the same cylinder is stored too
It meansThe cylinder is genuinely weak; test its injector next.
IfOnly P0284 is stored
It meansTest the injector, then the engine mechanically.
Step 2: Check the injector connector for corrosion or water, and compare the injector sound or signal with a neighbouring cylinder.
Warning:The engine is running with belts, fans and hot parts close to the injectors. A shop should do this with the engine running.
IfThe connector is damaged or the injector sounds or reads different
It meansInjector or its wiring is the likely cause.
IfThe injector looks and sounds normal
It meansCheck compression and leakdown.
Step 3: Run a compression test and a leakdown test on the cylinder and compare with the others.
Warning:Removing spark plugs and cranking the engine is hazardous on a hot engine or with fuel and ignition left enabled; leave it to a shop.
IfThe cylinder is more than about 10 percent off the others
It meansValves, rings or head gasket are suspect.
Points to: Mechanical wear in cylinder 8 (valves, rings, head gasket)
IfReadings are even
It meansAsk whether an injector was replaced and whether the learn procedure was done.
Points to: Injector learn procedure not done after an injector replacement
Symptoms
- Check engine light with slightly rough running
- Reduced power or fuel economy
- Misfire, stalling or a serious engine alert Gets more serious: stop and have it checked.
Compare with: Car shaking with the check engine light on
How to fix
Step 1: With the engine off and cool, check that the injector connector for that cylinder is fully seated and free of corrosion.
Step 2: Ask a shop to test the cylinder 8 injector against its neighbours before replacing anything.
Parts and cost context
- Fuel injector:Injectors are replaced one at a time or as a set after testing; labor varies, get a quote.
Labor varies by vehicle and shop; get a quote before you approve a repair.
Compare used part prices on PartPriceGuideOn your vehicle
We don't have reviewed vehicle-specific evidence for P0284 yet. The causes and tests above apply across vehicles.
Related codes
No curated relationships for P0284 yet.
Sources and review
- P0284 Cylinder 8 Contribution/Balance Fault
- On-Board Diagnostic Trouble Codes (generic code title list)
- Last reviewed
- Written by
- Saurabh K.
- Editorial review
- Pending
- Technician review
- Technician review pending
This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error