Cylinder Misfire in Ford engines: DTC P0300, diagnostics

The flashing Check Engine light warns the driver of malfunctions of the engine control system. In Ford engines, as in all modern injector cars, the engine is controlled by electronics. Testing the electronic control unit will help you understand what the error is. If the scanner or other diagnostic equipment indicates a P0300 error, it is most likely that we are dealing with a malfunction in the ignition system.

What are the symptoms of the DTC P0300?

DTC P0300 appears when the problem is related to the ignition. The error code can be defined in the range P0300-P0312. The values of the code depend on the number of cylinders and the fault of each cylinder. For example, error code 0301 indicates misfiring in the first cylinder, etc.

Even a dipstick knows that ignition without a flash is impossible. Especially under pressure and in difficult conditions, which is the combustion chamber. The quality of spark formation is the responsibility of the whole complex, from the spark plugs to the firmware of the electronic engine control unit.

Four-cylinder engines Ford, which are installed in the Focus, Mondeo, C-Max, Ford Fiesta are difficult to call trouble-free. Cylinder misfire is quite common in them, and it is expressed as follows:

  • engine thrashing;
  • vibration at idle, unstable idle RPM;
  • hard starting in cold conditions;
  • sagging in engine operation at medium revolutions;
  • sagging of traction at acceleration;
  • high fuel consumption;
  • appearance of errors during system scanning and a number of other symptoms.
P0300 on scanner screen, 2010 Ford Mustang

Consequently, Cylinder Misfire are temporary interruptions of spark formation on one or more spark plugs while the engine is running.

Cylinder Misfire can be either floating or stable. That is, the spark may be missing on only one particular cylinder, or it may appear alternately on several cylinders or on all cylinders at once.

Nevertheless, it is the P0300 code that is recorded by the scanner only when a spark formation failure occurs in several cylinders at once. The failure is not recorded instantly, but only 210 seconds after the next trigger at idle speed, at medium speed the frequency of the error should be at least once every 75 seconds.

This DTC ignition in several cylinders is indexed only when more than 3.25% of all flashes are missed. If a specific cylinder is at fault, we will see another variation of this code – 0301, 0302, or 0303, 0304 if we are dealing with a four-cylinder Ford engine.

Associated misfire errors in Ford engines

The most common errors are with codes:

  • P0300 – multiple ignition misfires irrespective of the cylinder, stray fault;
  • P0301 (P0302, P0303, P0304) – misfires on the first, 2, 3, 4 cylinders respectively;
  • Р0363 – due to ignition misfires, fuel supply is cut off in inoperative cylinders;
  • Р1301 (1302, 1303, 1304) – ignition misfires in cylinders that are critical to the catalyst;
  • P2301 (2302, 2303, 2304) – ignition coil circuit is shorted to the mass of the corresponding cylinder.

These faults do not appear immediately, but only after the third engine start since the initial detection of the problem. It is taken into account that code P0336 is not detected.

[stextbox id=’info’]For reference, DTC P0336 indicates a fault in the crankshaft position sensor circuit or the sensor itself.[/stextbox]

To self-diagnose these faults, it is enough to have an adapter ELM 327, which is freely available for sale, as well as to install on your cell phone diagnostic program. Independent primary diagnostics will help to find out exactly why the engine is tripping and where the Cylinder Misfire on the Ford Engines comes from.


Mechanic diagnose the DTC P0300

In fact, you do not need to be a great diagnostician and even have a scanner to determine the failure in the ignition system visually. If the check lights up and the engine rattles at idle rpm, rpm does not develop as before, jerks are noticeable when accelerating and starting up, you can talk about DTC P0300 or its derivatives even without a scanner.

wire damage
Ignition coil wire damaged

Any of the above problems is a wake-up call. Even if the electronic system did not signal for help, the driver should diagnose the systems himself and figure out what the car’s behavior is related to.

Causes of DTC P0300

Even a technician will not be able to give you one cause without a jump: it will require a complete diagnosis of the main systems, but since the fault is quite typical, the causes are more or less known. Here are the main ones:

  • Malfunctions in the fuel supply system, usually due to low-quality fuel or no fuel at all. The problem occurs when the filter is clogged and the pressure is low, as well as when the injectors are not functioning properly.
  • Errors in the ignition system. Any element directly involved in fuel inflammation can fail. More often than not, the problem involves faulty coils and spark plugs.
  • Problems related to the intake and exhaust. A common cause is a faulty catalytic converter clogged with debris. There is a possibility of problems in the valves.
  • Faulty electronic components. Lack of signal can cause an error to pop up. There may be problems in the whole electronic unit.

What must be checked

Although electronics have learned to do many things, they cannot replace human logic. The system simply states the fact of Cylinder Misfire, and why it occurred, you should think for yourself. First, let’s check the potentially suspect ignition system and check it out:

  • spark plugs;
  • high-voltage wires;
  • the ignition module or coils;
  • contacts in the ignition connectors and contacts on the electronic control unit.
ford coils
Ford Ecotec, ignition module

Since Cylinder Misfire can be related to more than just the formation of the spark, or rather the lack of spark, it is necessary to check the fuel system. It is possible that there is no ignition because there is nothing to burn in the cylinder.

However, we do not consider an empty tank. Let’s check further:

  • fuel for quality, there should be no extraneous odors, gasoline is homogeneous and without suspension, unfortunately, without a laboratory we will not check anything else, unless we drain all the fuel and fill it up with quality;
  • lean mixture, caused by air leakage;
  • clogged catalytic converter;
  • clogged injectors;
  • gasoline pump does not produce the required pressure;
  • clogged fuel filter;
  • Fuel leakage in the line.
2014 Ford Focus fuel injectors

In addition, check the compression in each cylinder. It should not be less than 10-12 atm and be the same (allowable difference of 3-5%) in each of the cylinders. Also check the accuracy of the alignment of the marks on the camshaft drive.

If nothing helped, everything is checked and everything is fine, and the DTC has not reset, check the electronic system. We start with the sensors:

  1. Airflow sensor.
  2. Detonation sensor.
  3. Crankshaft position sensor.
  4. The Camshaft Position sensor.

Tips for a detailed check

Check individual ignition coil and injector supply wires
  • Check the high-voltage wires. Use a multimeter to do this. Broken wiring is the source of problems if the values displayed by the meter fluctuate over a larger range. The normal resistance of the high-voltage wires is 4-10 kΩ.
  • Check the ignition coils or module. To check the coils, move them to a working cylinder: this will demonstrate that they are working. If the error code has changed to a different cylinder code, the faulty coil has been found.
  • Take a closer look at the spark plugs: check the electrodes for damage and fouling.
  • Use a diagnostic stand to check the injectors. Solving this problem on your own can lead to difficulties.
  • Check the intake manifold gasket: severe wear is one of the causes of malfunction.
  • Take a closer look at the long-term fuel correction value for different cylinders. A stuck valve will also signal an error. If the parameter is very different from ideal, (by more than three percent) consider solving the problem.
exhaust system
Ford Exhaust System Diagram

If the points have been completed, the system is normal, and the DTCs remain, there is a high probability that the problem is in the injector circuits. In this case, the engine may malfunction when cold. The appearance of the malfunction is sometimes a sign of the failure of a pair of wires. Thus it is possible to make an attempt to diagnose and replace the failed parts, saving on a visit to the service station.

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