How to adjust idle speed
The first engines of the pioneers of the automotive industry did without idling. The invention of the carburetor and ignition advance made it possible to reduce the speed threshold for stable engine operation through special mixture formation. The design of modern cars provides for idling (XX) in the range of 500-1000 rpm, depending on the type of engine. For diesel engines with their active “bottoms”, it is less, for gasoline engines it is more. When adjusting the XX, losses on the operation of electrical consumers and attachments (power steering pump, air conditioner) are taken into account, as well as, on machines with automatic transmission, the need to create working pressure in the torque converter.
WHY ADJUST IDLING
Idling is a compromise mode of engine operation. Raising the idle speed leads to an increase in fuel consumption and increased heat transfer from the engine. But an excessive decrease in the speed of the twentieth has even greater disadvantages:
deterioration of ventilation of exhaust gases;
problems with filling the cylinders with fresh mixture;
reduction in oil pressure.
This can lead to deposits, increased engine loads, reduced engine life, and premature failure of its components: piston group, crankshaft, catalyst, and spark plugs. In addition, low idle speeds lead to vibrations, to environmental parameters going beyond the norm. Finally, the lower the engine speed, the higher the risk of stalling when the load increases (suddenly pressing the gas pedal).
PRINCIPLES OF ADJUSTING XX ON DIFFERENT ENGINES
Since the principles of fuel supply vary significantly depending on the type of engine, idle adjustment is carried out in different ways:
for diesels;
for gasoline carburetors
and petrol injection engines.
For diesel engines, the XX is adjusted at the injection pump (high pressure fuel pump) by limiting the fuel supply. It should be noted that for diesel engines, not only the minimum idle speed is adjusted, but also the maximum engine speed, as well as, in some cases, the fast idle speed.
In the process of adjusting the speed, 4-5 adjusting screws are involved. The adjustment is carried out approximately according to the same principle as the adjustment of the clutch pedal: the speed is adjusted with a screw, after which it is tightened with a lock nut. Before the procedure, it is necessary to change the filters, warm up the engine and set the fuel injection advance angle.
On carbureted gasoline engines, the idle speed is set using two adjusting screws: the mixture quality screw and the mixture quantity screw. In addition, you need to pay attention to the performance of the jet XX (solenoid valve), if necessary, clean it and troubleshoot the electrical part. Also, as in the case of a diesel engine, the adjustment is carried out on a warm engine, and before it you need to check the ignition system: advance angle, candles and high-voltage wires.
Injection (injection) gasoline engines do not require idle speed adjustment as a separate regular procedure. However, from time to time they also have problems with idling, which indicates malfunctions of the engine systems. In this case, you need to carry out computer diagnostics of the car, paying attention to the following:
ECM sensors - electronic engine management system. Incorrect data coming from them can cause incorrect fuel supply or ignition system operation.
Air leak in abnormal places. It can be the cause of the lean mixture, therefore, a decrease in speed.
Fuel injectors, spark plugs and ignition coils and other factors leading to unstable operation of the internal combustion engine - tripping, etc.
Filters - air and fuel.
Throttle body - it may be dirty. It must be remembered that in many injection cars (especially those equipped with an electronic gas pedal), after cleaning, the throttle valve needs to be adapted (trained).
If all these systems are in order, it is necessary to check the IAC - idle speed control. It may need cleaning, replacement of components: guide bushing, needle, or be completely inoperative.
It should be noted that most of the above works require certain qualifications and experience, so it is not easy to perform them on your own. In order to qualitatively adjust the idle speed of the engine, it is better to turn to professionals - for example, to any of the service stations of the Wilgood smart car service network.