Black Smoke from Exhaust — Engine is Running Way Too Rich

What's happening

Black smoke = excess fuel. Modern fuel-injected engines target a 14.7:1 air-fuel ratio. When that ratio drops well below (more fuel, less air), the extra fuel doesn't burn and exits as black soot. Diesels can show black smoke under heavy load normally; gasoline cars showing black smoke have a fuel-system problem.

You might also notice

• Strong fuel smell from the exhaust
• Bad fuel economy
• Rough idle, stumbling
• Fouled spark plugs
• Catalytic converter overheating

Likely causes (most common first)

1. Leaking fuel injector(s) — stuck partially open
2. Failed fuel pressure regulator (returnless system) feeding too much pressure
3. Failed MAF sensor under-reporting airflow
4. Failed MAP sensor stuck high
5. O2 sensor stuck reading lean (ECM compensates by adding fuel)
6. Restricted air filter or intake (less air in)

What to check first

1. Read codes — P0172 / P0175 / P010x are the headline suspects
2. Pull the spark plugs — sooty black plugs confirm a rich condition
3. Check the air filter for restriction
4. On scan tool, watch fuel trims — heavy negative LTFT confirms rich

Common OBD2 codes for this symptom

Don't have the code yet? Look up your code or read it with AXLY.pro.

Can I keep driving?

Drivable but you are wasting fuel and damaging the catalytic converter every minute. Fix soon.

Confirm with the actual code

Symptom-based diagnosis narrows the field — reading the actual stored code finishes the job. AXLY.pro is a free iPhone app that pairs with any Bluetooth OBD2 adapter and reads every stored DTC.