The correct firing order of the Ford 4.6-liter V8 is essential for its smooth operation. It is an efficient and reliable engine available in the F150, and other medium-duty trucks in the F series.
What is the Firing Order for a 4.6 Ford? Ford 4.6 has 8 cylinders arranged in a sequential pattern from front to back in 2 banks of 4 cylinders on each side. It has a firing order similar to all Ford V8 engines except Coyote 5.0. The sequence in which ECM fires spark plugs in Ford 4.6 V8 starts with cylinder # 1 on the left front, then cylinder # 3 on the same side, next cylinder # 7 on the second bank on your right side. Next, it fires cylinder # 2,then cylinder # 6, next cylinder # 5. At the end of the order are cylinder # 4 on the left-back and cylinder # 8 on the right backside.
Ford 4.6 is a V8 modular engine having 8 cylinders and therefore 8 spark plugs. They have an arrangement of 4 cylinders in a row placed at an angle of 90o to the second row.
Cylinder numbering starts from 1 to 4 on the left bank from front to back. At the same time, it is 5 to 8 on the right bank from the front radiator side to the back.
The firing order of the engine by keeping in mind the cylinder numbering is 1-3-7-2-6-5-4-8.
To make it simple, we write it by classifying cylinders on the left bank as the letter Lx with x representing its position and on the right as Rx.
It means cylinders or spark plugs on the left bank will be from L1 to L4 from front to back, and on the right bank will be from R1 to R4 from front to back. The firing order for Ford 4.6 in such classification will be L1-L3-R3-L2-R2-R1-L4-R4.
How does the firing order for a 4.6 Ford work?
You will find 2 types of ignition control systems on Ford 4.6 modular engine designs.
- Waste spark ignition system
- Coil-on-plug system
Waste spark system
Earlier versions of the Ford 4.6 have a waste spark ignition system controlled by its ECM.
You will find 2 coil packs installed on the engine. Each group has 4 wires connected in a pattern to the respective spark plugs on cylinder banks.
It is known as waste spark system because ECM sends a signal to 2 cylinders simultaneously even though only one requires ignition while the other is on the exhaust stroke.
Therefore, spark energy to that plug wastes out. Due to simultaneous controlling of 2 plugs, you will find 4 signal wires from ECM to the coil packs.
In the Ford Mustang 1999 model, Ford introduced coil-on-plug ignition systems. In this design, there is a separate coil for each spark plug. ECM directly controls each of them without any distributor coil involved in the middle.
Therefore, you will find 8 wires from its control module to all spark plugs on all cylinders. It is also called a distributor-less ignition system.
A sensor on the crankshaft or camshaft senses its position to determine the next piston coming up to the top dead center (TDC) and requires ignition.
It sends a signal to the ignition module on ECM. ECM triggers the coil for the respective spark plug, and it fires. ECM then repeats the procedure in the predefined order saved in its memory.
Do all Ford vehicles with 4.6 engines have the same firing order?
All Ford vehicles with 4.6-liter V8 engines have the same firing order for spark plugs from pickup trucks to cars.
It is a feature that ensures the smoother, noiseless operation of the vehicles with maximum power extraction from the engine.
In addition, all newer Ford V8 engines in the modular family have the same firing order, irrespective of their displacement length except the 5-liter Coyote engine.
What causes the incorrect firing order in Ford 4.6?
There can be several reasons for a weird firing order on Ford 4.6.
The main components responsible for the proper sequence of spark plug activation are plug coils, signal wiring from the computer, distributor connections, crankshaft/camshaft position sensor, and spark plugs.
Faulty wiring to spark plug
Engine computer or control module sends signals to spark plug coils through distributors or direct connection depending on the ignition system.
For example, it can activate when the valve is closed or the piston is in exhaust position.
The damaged crankshaft position sensor
The crankshaft/camshaft position sensor tells the ECM regarding the position of the first spark plug to be fired.
If it is faulty or sends a signal with erroneous information, the computer will start firing the incorrect spark plug, and the whole order will be disturbed accordingly.
Damaged spark plug
The spark plug should be in working condition to ensure a proper firing pattern. In case of a faulty spark plug or its misfiring, you will get a firing order with skipped positions of the faulty cylinders.
You will observe the symptoms like vibrations, noisy operation, and failure to start the vehicle.
In Ford 4.6 modular engine, a computer or ECM controls all spark plugs with the help of sensors, spark coils, and pre-programmed patterns in its memory.
A faulty ignition module or coil packs can incorrectly activate spark plugs, resulting in all associated problems already discussed.
Disadvantages of incorrect firing order in 4.6 Ford
Engine designers fix the firing order to maintain engine balance and reduce the excessive vibrations.
However, changing it in an irregular sequence due to a fault or intentionally can result in problems like misfiring, failure to start, noisy engine sound, excessive vibrations, and poor power characteristics.
Failure to start
In case of a wrong or delayed firing order, the engine will not perform according to the intended pattern.
It has a sequence of steps from valve opening, injecting proper air to fuel mixture, its compression, and then spark plug firing.
Often you hear an engine running with a big sound like a bang. It is a result of ignition in the intake manifold or exhaust chamber and is called backfiring.
If, due to some reason, the wiring sequence in the distributor changes, it will disturb the complete order, and you will get backfiring, resulting in waste of fuel, power, and damage to engine parts.
Poor engine performance
The correct sequence is mandatory to deliver maximum power to the crankshaft. Each cylinder fires up a predefined time in a sequence adding in the total capacity.
In an incorrect order, misfiring, backfiring, or no firing results in poor engine power characteristics. Moreover, you will also observe rough idling failing to perform efficiently.
Bad engine sound
The wrong firing order of spark plugs produces a noisy operation. The possible reasons are backfiring, incomplete combustion, the collision of pistons with valves, and simultaneous firing of 2 cylinders.
You should maintain a proper sequence of spark coils and maintain the timing belt or chain.
If all cylinders fire simultaneously, you will get maximum power at that moment and no power in the next instance.
Therefore, it will result in jerky engine operation. Moreover, smooth distribution of energy throughout the combustion cycle is imperative through a proper firing order.
The design of the crankshaft also depends on this sequence of spark plugs activation.
If there is any problem with this sequence, you will observe jerky, imbalanced, and random motion full of vibrations.
Does the firing order depend on the cylinder numbering?
The firing order is independent of cylinder numbering. Instead, it uses cylinder numbering to mention the positions of spark plugs that will fire next.
Therefore, both are different parameters and serve their purposes.
Can you change the firing order on the Ford 4.6 V8 engine?
You can change the firing order on Ford 4.6 engines by swapping the signal wires from ECM to coil packs in coil-on-plug systems.
While in the ignition system with the distributor, you need to change the connection order over there.
However, this modification can result in negative impacts like reduced engine performance, increased vibrations, or damage to its parts. Therefore, do it only if you have a complete understanding of its consequences.
How to check the firing order of the Ford 4.6 engine?
Yes, you can check the firing order by manually moving it to observe the movement of valves.
First, open the valve cover and bring the piston in cylinder #1 to the top dead center (TDC). Then rotate the engine clockwise and observe the intake valves.
What causes crossfire between the spark plugs on Ford 4.6?
When two spark plugs have adjacent positions on the engine and in the firing order like 5 & 6 on Ford 4.6, running their wires parallel for a long distance can cause a problem.
Active wire can induce emf in the second coil causing its activation. Therefore, you can observe premature ignition on the next spark plug and bad engine sound. To prevent it, twist the wires together to both coils to cancel their magnetic fields.