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  Today we are covering what is required to carry out a basic tune-up on an engine equiped with electronic fuel injection. This type of tune-up is considered part of routine maintenance for your vehicle and should be carried out every 10,000km (6250miles) or at 6 month intervals. As the name suggests we are only covering the basics with this article and there is many other aspects to tuning an EFI engine, but we are aiming for the things that everyone can do in their backyard or garage with only basic hand tools and limited knowledge. So here we go!

Parts/Tools Required.

1. Spark Plug Socket and extension bar and Ratchet. There are two sizes of spark plugs - 5/8 and 13/16.
2. A foot long piece of hose or telescopic magnet for retrieving spark plugs that are deep in the cylinder head.
3. The necessary tools to remove the fuel filter on your particular vehicle. NOTE - On screw in fittings use pipe spanners only not open end spanners.
4. Can of Throttle Body Cleaner or Carby Cleaner (has to be ’sensor safe’)
5. Replacement Air Filter, Fuel Filter, Spark Plugs and Plug Leads if needed.
6. Couple of rags.

Doing the job.

1. Inspect Air Filter. The cleaner the better here! Also check the air intake for splits or cracks and the air filter box for foreign material.
2. Remove the air intake and thoroughly clean the throttle body bore and throttle plate by spraying with Throttle body cleaner. A rag placed directly underneath the throttle body stops the muck from going all over your driveway. NOTE - the vehicle will take longer to start and will run rough until the engine burns all the Throttle Body Cleaner - don’t stress this is normal! Refit air intake and air filter once done.
3. Remove fuel filter. Drain the fuel from the filter in the opposite direction to which it normally travels. If it comes out black or has contaminates in it replace the filter.
4. Remove and inspect the spark plugs. Be sure to note where each spark plug lead goes and which plug came out of which cylinder. The spark plugs can tell you a lot about how your engine is running. A brown or greyish-white colour on the insulator nose indicates good engine condition. A dry, black insulator nose and electrode indicates a rich fuel mixture possibly caused by a clogged air filter, faulty oxygen sensor or engine temp. sensor and the list goes on! A wet, black, oily insulator nose and electrode indicates the engine is burning oil. Potential causes can be worn piston rings, valve guides or seals or engine oil level way too high. If the insulator or electrode seems overly worn or the plugs are suffering from any of the above symptoms, a new set will help keep the engine running well until the problems can be addressed.
5. Remove the disributor cap and check for cracks between the terminals. Also check the rotor and remove any build-up with emery paper. Remove the spark plug leads one at a time and check the contacts in each end and remove any deposits if nescessary. Check the leads for cracks or perishing and replace if nescessary.
6. If you have access to a timing light and the correct procedure for checking timing on your particular vehicle this would be a good time to do this. As different manufacturers use many different ways to check ignition timing this will not be possible without the correct information.
7. Start the car and allow some time for the Throttle Body Cleaner to pass through the engine and then it’s test drive time. If you needed to replace a few parts you will notice a big difference in how the car runs, sometimes just cleaning the throttle body can make a huge difference to how the vehicle performs.

  That covers our basic tune-up for now. Further down the track we will look at some specific engine problems such as mis-firing and poor fuel economy and their likely causes. Until then take care and be safe on the roads.

Craig

  EFI or electronic fuel injection has been with us for quite a while now and has proven to be far superior to the old carburettor. The easiest way to describe how it works is that inputs recieved from various sensors around the engine (and sometimes transmission) send a signal to the ECU or electronic control unit, the control unit processes these signals and sends an output to the fuel injectors, air bypass valve and on distributor-less engines, the coils. Lets take a brief look at the input, output and control unit functions of a common multi-point type injection system used on most main-stream cars today. To simplify this post ( and not bore the hell out of everyone ) we will leave the ‘hardware’ side of things to another day.

  Most input or information sensors are resistors that modify the voltage applied to them by the computer, this voltage is called the Reference Voltage. The computer sends this reference voltage to the sensor and as the resistance in the sensor changes so does the return voltage to the computer. The ECU or computer then uses these changes in voltage to make the necessary adjustments to keep the engine running at it’s best. Typical input sensors found on todays vehicle will include;

• Airflow meter - placed in the air intake tract and used to measure the amount of airflow and adjust the fuel delivery appropriately.
• Manifold Pressure Sensor - often referred to as MAP sensors and used in place of air flow meters to determine the load on the engine and the fuel required to keep it running.
• Air and Coolant temp. sensors - used to provide a rich air/fuel mixture for starting and warm-up and to measure air density which affects air/fuel ratio.
• Oxygen sensor - regarded as the most important information sensor. Located in the exhaust pipe or manifold. Used to measure the amount of oxygen in the exhaust gasses, an indication of whether the engine is running lean or rich.
• Throttle Position Sensor - tells the computer whether the engine is at idle or wide open throttle or any position in between. Once again used to calculate the amount of fuel required.

  The ECU or computer is the brain that processes these voltage signals and adjusts the outputs in accordance with it’s program or ‘map’.

Typical outputs are;

• Fuel Injectors - the principal component in the output system. The computer reads from the input sensors and calculates when the injector should open and for how long to maintain the ideal air/fuel ratio.
• Air bypass valve - used to correct idle speed and air/fuel mixture at idle. Allows air to bypass the closed throttle body butterfly.
• Coils - on a distributor-less ignition the computer is used to ‘fire’ coils that are located either on top of the spark plug (via an insulator) or close by with a small plug lead. The instant the coils are fired can be dependant on engine speed and load.

  That sums up our brief look into the EFI system. Obviously this is only a basic overview of things, but my idea was to give you an understanding of how and why it works. And besides, I could write a whole book once we get into the nitty-gritty of it all!

Take care and be safe on the roads.

Craig

We have moved the RA28 Celica - 1GGTE conversion page to the Photo Gallery. There are plenty of photos of the build and if you require any more information please don’t hesitate to shoot us an email to autofix@aapt.net.au