6 Most Common Problems with Ford 4.6L Engine

Ford's 4.6L engine was an improvement over the 5.0L 302 pushrod engine that it replaced. The 4.6L can last well over 100,000 miles when properly maintained. 

Ford's 4.6 engine is straightforward to work on due to having a very open and well-designed top. For example, it is effortless to access and replace the spark plugs, coils, and wiring harness. Replacing injectors is very simple as well.

Common Problems

1. Engine Missfire

Check engine light on with misfire codes p0300 – p0308 are most common due to spark plug or ignition coil failures.

If you have the P0300 random misfire or undetected misfire, Ford has released a powertrain control module update to fix this problem. 

2. Injector Problems

There were a few instances of injectors clogging or sticking open and causing P0172 or P0175. When reading the fault codes via the OBD-II port, you'll notice that fault codes point to faulty oxygen sensors.

Often injector problems are miss diagnosed as oxygen sensor problems. The oxygen sensors are reporting to the PCM what they are detecting. These codes are the management system saying that the exhaust is rich or past its limit. A common symptom is a black smoke at engine start-up. That is a sure sign of a leaking injector.

If this problem is ignored for a long time, catalytic converter failure is next because of overheating and melting. Eventually, the driver may notice excessive causes backpressure, check engine light flashing, and poor performance.

3. Fuel Pressure Regulator

Fuel pressure regulators located on the fuel rail could leak out their supply vacuum port with raw fuel. If you suspect a fuel injector or a leaky regulator, use a fuel pressure test gauge to perform a leak-down test or a diagnostic scanner that can do an injector test.

This is a fire hazard. Take precautions or have a professional do this for you.

If you have one that melts or the sensor is melted, make sure to have the exhaust system checked for excessive backpressure. It’s a good possibility there was a misfire or a leaking injector in the past, even if a misfire isn't present currently.  

4. Exhaust Gas Recirculation Problems

Exhaust gas recirculation system may fail and set codes:

• P1408: EGR Out Of Self-Test Range
• P0401: Exhaust Gas Recirculation (EGR) Flow Insufficient Detected

Generally, p1408 or p0401 are exhaust gas recirculation system codes.

The P0401 was usually a faulty DPFE sensor (EGR pressure differential sensor). The DPFE sensor could get moisture from condensation in the exhaust system and fail, or the hose from the exhaust bleed fitting could fall off or melt.

5. Oil leaks

Overall the 4.6L Ford engine does not suffer from major oil leaks.

They were occasional valve cover gasket or front crankshaft seal leaks. 

Ford 4.6L engine was used in police interceptor as well, in which case the oil coolers often leak externally or into the cooling system. Replacement of the cooler and chemical flushing the cooling system took care of that.

6. Front cover noises

Timing chains guides and tensioners would fail if maintenance were not done at proper intervals. Oil changes with filter and just plain common sense would keep this engine going for a long time.

It is strongly recommended to use quality fuel to keep it running smoothly. Keep in mind that it is not necessary to use higher octane fuel. 

Any vehicle equipped with a Ford 4.6L engine can last a long time. Many are installed in police interceptors cars, which often lasts a very long time. The odometer in the 250,000-300,000 range is not unheard of in a Lincoln Town Car or F-150. Overall, Ford's 4.6L engines are very dependable and reliable. 

Applications

• Ford Crown Victoria
• Ford E-Series
• Ford Expedition
• Ford Explorer
• Ford Explorer Sport Trac
• Ford F-150
• Ford Thunderbird
• Lincoln Aviator
• Lincoln Continental
• Lincoln Mark VIII
• Mercury Cougar
• Mercury Grand Marquis
• Mercury Marauder

Specifications