Electronic Diagnostics: Ford Focus 1.8 petrol
With Visteon System 7 type ESU 121 management system.
Making its European debut in 1998, Ford’s Escort replacement, the Focus, initially received mixed reviews for its idiosyncratic styling, yet was almost universally praised for its dynamism and comfort. Successive generations have become more conventional in appearance and, 20 years down the line, the Focus remains a family and fleet favourite, for both new and used examples. At various times during the last decade it has been the best-selling car in Britain, and sometimes the best-seller globally, too.
Second-generation models arrived for 2005, with mildly-restyled body panels, lamps and front grille introduced late in 2007. The Focus MKIII arrived in 2011.
Over the years, a wide variety of petrol and diesel engines have powered the Focus, including direct-injection, twin overhead camshaft, four-cylinder Duratec petrol units, first dating from 2001 (and part of the Mazda L engine family). This is the engine in the Focus featured here, a second-generation, 1.8-litre (engine code QQDB) petrol model registered in March 2010. This model features a combined igniton and fuel Engine Control Module (ECM) from Visteon.
Our guide to this model’s engine and its system is Edward Haggar.
Preparation
At the outset it is worth mentioning that this engine operates under a partssaving wasted-spark ignition system. In this, two spark plugs are fired at the same time in pairs: one plug fires on the compression stroke, igniting the fuel mixture and producing power, while the plug on another cylinder fires simultaneously on the exhaust stroke, this has no effect on engine power and is thus said to be ‘wasted’.
In addition, this Focus features a Smart Charge alternator, which varies the level of battery charging according to the temperature of the engine, delivering a higher rate of charging at lower temperatures. It is important to never jump-start a car with a Smart Charge set-up if the battery is discharged. This is
because the system may supply up to 18 volts, potentially causing major damage to electrical components/modules on the vehicle. It is also important to note that vehicles with Smart Charge systems require special enhanced flooded types of battery (EFB); normal lead-acid types will not do the job.
Note that there is no cambelt to renew on this engine, as it features a chain-driven camshaft.
This Focus employs an accelerator position sensor mounted on the throttle pedal. Like most recent vehicles, it has a fully electronic link between the pedal and the throttle body, as opposed to the mechanical connection on older cars. The information gathered by the sensor is sent to the ECM so the required level of fuel/ air mixture can be supplied to the engine.
The inlet manifold incorporates throttle flaps that move in response to the accelerator pedal position. Throttle flap cleaning is possible if performed with care using a non-aggressive cleaning agent and a small brush.
Another vital component of the management system on this Focus is the coolant temperature sensor. This assesses the temperature of the coolant, indicating how warm the engine is and delivering this information to the ECM, which can then calculate and control appropriate/ optimum fuel delivery (see Fault 3).
The mass air flow (MAF) sensor in this Ford assesses the rate of air flowing through the intake system. The data is passed electronically to the ECM, which then uses the information to calculate and adjust the required levels of fuelling.
It is essential that the pressure within the inlet manifold is precisely assessed, with the mass absolute pressure (MAP) sensor carrying out this task. Again, the information is fed through to the ECM as a vital part of the fuel requirements equation.
Note that, in Ford terminology, the ECM is known as the Powertrain Control Module (PCM).
Fault 1 IGNITION COIL FAILURE
Symptoms of our first fault on this Focus include misfiring, poor running and possible cutting-out of the engine. The car will be undriveable and the engine warning light will be illuminated, with fault codes stored for relevant cylinder misfires. This could be due to failure of one or more of the four separate ignition coils – with this engine one individual coil serves each spark plug.
The first diagnostic step should be a fault code check. Fords are really good from a diagnostic point of view and a basic EOBD reader will show codes. You will see fault codes relevant to the failed cylinder.
Examples of these engines that are poorly maintained can suffer from valve or piston ring issues. Always remove the
spark plugs and check for arcing, but also pay attention to the tip for signs of oil and excessive carbon build-up.
If suitable test equipment is available, carry out a cylinder leakage check or compression test – in each case you are looking for obvious drops. If all is OK on this front, you can then inspect the ignition coils. A quick check is to swap the coil from one cylinder to another, noting if the misfire moves to that cylinder. A more in-depth test involves using an oscilloscope to check primary and secondary circuits.
A less common fault is corrosion in
the rear of the coil plug. In some cases, damage occurs to the seal, allowing moisture ingress and corrosion.
If a new plug is required, a secondhand connector is inexpensive, but it will need to be soldered in. Don’t be tempted to use normal connections because, over time, moisture will find its way in. Where available, always use solder in conjunction with heat shrink for an air-tight seal.
Due to the high volumes produced, genuine Ford parts are usually relatively inexpensive – a decent branded coil can be bought for around £20. If finances allow, it is advisable to renew all four
coils at the same time – remember that the other three are the same age and will have covered the same mileage as the one that has failed.
Fault 2
DEFECTIVE OXYGEN SENSOR
When our next fault arises, most of the time the driver will only be aware that the engine warning light is on, but that the car is driving faultlessly. In this situation, the first thing to do is carry
out a diagnostic investigation and read the stored fault codes – you will see a code related to ‘oxygen sensor heater circuit open circuit’.
The next step should be to remove the connector – it is only clipped in place – and inspect it for corrosion. We’ve come across a Focus where the clip was broken and the connector was left hanging, allowing water to enter and sit within the connector, corroding away the pins.
If all is OK so far, use a multimeter to check the heater wires for resistance – you will likely find an open circuit, meaning a new sensor is required. Before installing the replacement sensor, ensure the threads are clean to ensure a tight fit – a sensor that doesn’t sit flush can allow air to be drawn in, causing other issues.
Note that a special oxygen sensor socket is a essential to aid fitting and removal, but they can be bought cheaply. If finances allow, change both pre- and post-cat sensors – the other sensor might be the same age and mileage, thus could be on borrowed time.
Fault 3
AILING COOLANT TEMPERATURE SENSOR
The symptoms relating to our third fault are extended cranking times and a strong, fuel-rich smell coming from the exhaust – plus, if it’s MOT time, a failure due to excessively high CO readings. Diagnosing this without a bit of experience can lead people down the wrong path and they’ll fit new parts that aren’t required.
Carry out a full diagnostic check. It’s unlikely this will show any faults with the coolant temperature sensor, because the way the sensor works means it will still be operating within its parameters, so the ECM won’t trigger a fault. You will probably find codes relating to ‘oxygen sensors rich mixture’, which is where the inexperienced would fit a new oxygen sensor. Live data now can be a real help, if available. Look up coolant temperature and you will find that the engine is cold but the reading will be high or vice versa – it’s possible that it can fail either way.
The coolant temperature sensor is located on the right-hand side of the cylinderhead in the coolant housing – it goes without saying that you need to ensure that the cooling system is drained before attempting to renew the sensor. It’s not uncommon for this housing to leak as
well, so it might be worth replacing it at the same time as the sensor.
Always ensure that red long-life coolant is used. These systems don’t require any special bleeding and usually bleed out OK. To start with, always fill the system to the ‘Max’ mark. Set the heater controls inside the car to ‘Hot’, start the engine and run it until the top and bottom hoses are hot; a digital thermometer can make temperature assessment easier.
Once both hoses are hot, put on the pressure cap and wait for the cooling fan to operate. After this, stop the engine, allow the engine to cool and re-check the coolant level. It goes without saying to never remove the cap when hot.
Fault 4
INCORRECT SPECIFICATION ENGINE OIL
Using the wrong engine oil doesn’t just affect Fords, but vehicles from every manufacturer. At one time there
were just three grades of engine oil in the workshop: 10W-40, 15W-40 and 20W-50. Now garages typically stock 10 different types, with extended change intervals and lower emissions, so using the right oil is crucial.
With regards the Focus, we have encountered examples where the driver complains of poor acceleration and what might be described as a misfire not long after the car has been serviced. In fact, it is the tappets sticking that causes these problems. If the trouble is identified at an early stage, a good engine flush and oil change using the correct oil can sort things out. However, if the engine is left running with the wrong oil, internal scoring and excessive wear will arise. Lack of the correct lubrication will result in hefty repair bills.