1. Malfunctions of the ignition system that cause interruptions in the operation of the engine or stop it include the following:
- current leakage through cracks or burnouts in the rotor or ignition distributor cover. What is usually done with such details? They are replaced with new ones;
- burning of the contacts of the cover or rotor of the ignition distributor. Such contacts are cleaned with a velvet file or a special abrasive plate for cleaning contacts, washed with gasoline and blown with compressed air;
- damage to the candle or candles. Characteristic features: dark skirt of the insulator, lower temperature of the candle body. If you remove the wire from «suspect» candles with the engine running, the last nothing «won't feel». Candles that fail to work are usually replaced with new ones. It happens that by replacing one or two candles, you did not get tangible results;
- burning of the runner resistor. The thing is, you can't see anything visually. A burnt resistor does not give itself away. If you are on the road and there is no new slider at hand, temporarily the role of a resistor can be played by a piece of wire wrapped around the spacer plate of the slider or bent in the form of a bracket inserted in place of the resistor. Such manipulations do not always ensure success;
- failure of the distributor capacitor. To verify this, you must remove the distributor cap, disconnect the capacitor wire and turn the crankshaft (using the crank or a special key to turn the crankshaft for the car VAZ-2105 and VAZ-2107) until the contacts are completely closed. Having completed these preparatory operations, turn on the ignition, bring the central high voltage wire to a distance of 4-5 mm to the capacitor wire. Manually open the breaker contacts 3-4 times (this way you charge the capacitor, if it is serviceable) and then bring the tip of the capacitor wire to «mass». If the capacitor is good, a click will be heard, i.e. the capacitor will be discharged. The absence of a click is a reason to replace the capacitor;
- violation of the installation - the moment of ignition;
- changing the gaps between the breaker contacts;
- wear of the sleeve or weakening of the spring of the movable contact of the breaker, large runout of the distributor roller or wear of the roller sleeve. Performing these operations requires a certain skill, so it is advisable to turn to specialists.
2. Violation of thermal gaps between the levers and camshaft cams significantly affects the smooth operation of the engine. With increased clearances, mating parts wear out much more intensively. At very small gaps, the valves are cramped, they are clamped and their «protest» express with pops or shots from the silencer and carburetor in the same way as with «shot down» ignition. Small gaps (less than 0.15 mm) can cause a lot of trouble, since burning of valve plates or deformation of the rods is not excluded.
3. One of the most likely culprits for erratic engine performance is the carburetor. All of its many parts and assemblies, mechanisms and systems can be the reasons for the engine to work intermittently. If the jets or carburetor channels are clogged, the timely and precisely dosed supply of fuel, air and combustible mixture is immediately disrupted. As a result, starting a cold engine is difficult, power is lost. Engine operation, especially at high engine speeds, becomes unstable. If the idle jets are clogged (pic. 44), this will immediately affect the start-up of a hot engine and its idling.
Pic. 44. Scheme of the carburetor idle system:
1 - cover of the carburetor body; 2 - air jet of the idle system; 3 - fuel jet of the idle system, 4 - fuel channel of the idle system; 5 - pneumatic valve; 5 throttle valve of the primary chamber; 7 - air supply channel; 8 - forced idle economizer; 9 - a hose connecting the economizer with a pneumatic valve; 10 - adjusting screw for the amount of the mixture; 11 - adjusting screw for the quality of the mixture; 12 - emulsion channel of the idle system; 13 - adjusting screw for factory adjustment of the carburetor.
Sometimes the pollution of jets and channels is so old that compressed air is indispensable here. Surgery is required. This piece of jewelry. Millimeter holes have to be soaked in acetone, cleaned with sharpened wooden sticks, and then washed in gasoline. Patience and precision are required. But such a thing should be done when there is no other way out. Most jets are removable and can be replaced with new ones, especially since there are special repair kits for carburetors on sale, which also include jets. If new jets are available, special care must be taken to install the exact jet required. Primary jets (p. to.) and secondary (V. To.) carburetor chambers have calibrated holes, the values of which are given in table. 3.
On jets and sprayer bodies there are numbers indicating the diameter of the hole in hundredths of a millimeter. So, 150 means that the diameter of the jet is 1.5 mm. There is also a marking on the body of the atomizer corresponding to the conditional diameter of the channel section through which the emulsion leaves the main dosing system.
The appearance of water in the carburetor has about the same effect as clogged jets. The presence of water is especially unpleasant in winter. Regardless of the time of year, water must be removed, and not only from the carburetor, but also from the fuel tank, since all the troubles come from it. To rid the carburetor of water, it must be removed and blown well with compressed air. As for the fuel tank, you can not remove it, remembering that water is heavier than gasoline and will always be at the very bottom.
Another reason that causes unstable operation of the engine at idle is air leakage through places such as the connection of the carburetor with the pipeline, the cylinder heads with the intake pipeline, through the hose that goes to the vacuum brake booster for cars of the VAZ-2103, -2105 model, - 2106, -2121, -2107. This defect can occur only in two cases: either the parts are loosened, or the gaskets (hose) deformed. First of all, it is necessary to tighten the bolts, nuts and clamp in the indicated connections. If these actions do not achieve anything, you will have to change the gaskets or the hose, depending on where the air is sucked in.
Quite often, the cause of unstable idling is a faulty solenoid valve. Sometimes specks get into the idle passage at the valve. To remove them, some motorists use a simple but effective method: they slightly unscrew the solenoid valve and wrap it again.
All these operations are carried out with the engine running (at a crankshaft speed of 2000-2500 rpm).
Speaking of the solenoid valve, motorists should be advised to turn to the experience they have already gained in restoring the valve on their own if it is not possible to purchase it.
Often the valve fails due to oxidation of the casing in the place where it fits in the contact plate. Repair consists in the removal of oxidation products and only, therefore, the desire of motorists to revive the valve's performance is quite understandable. With a sharp screwdriver, carefully flare the casing from the side of the plug, remove the coil, clean the oxidized areas with sandpaper, and then return the coil to its place.
The casing is again rolled up and filled with BF-2 glue.
Sometimes, when idling, the engine of the VAZ-2105 and -2107 cars suddenly starts to spontaneously increase the speed of the crankshaft, then resets them, or even refuses to work at all. This is usually caused by a malfunction of the pneumatic valve 5 (see fig. 44) forced idle economizer (EPHH).
If this happens without a new valve, disconnect hose 9 from the valve to the carburetor and plug it.