Often the causes that cause unstable operation of the engine at idle can also be the causes of unstable operation of the engine and at high crankshaft speeds, clogging of fuel lines and jets, the presence of water in the carburetor and a malfunction of the ignition system - each of these reasons can disrupt the stable operation of the engine at high engine speeds. any mode. Therefore, the fault detection and elimination circuit should be the same: fuel lines - fuel pump - carburetor - breaker-distributor - high voltage wires - candles.
There are concepts: «glow number» and «glow ignition». If, due to inattention, candles were installed on the car that did not meet the manufacturer's recommendations, and even more so that they did not correspond to the glow number, the occurrence of the described defect is guaranteed. Having warmed up, the engine starts to work to the accompaniment of metallic knocks, similar to detonation. However, in this case, it is a glow ignition. Drivers often confuse these two different processes - detonation and self-ignition. Self-ignition (glow ignition) usually occurs with engine overheating, when the mixture compressed in the combustion chamber ignites from high temperature until a spark appears. «Arsonists» there may be hot electrodes or soot particles. The glow plug is easy to check. Switch off the ignition. When working with detonation, the engine will immediately stop. With glow ignition, it will still work. Naturally, the engine must be stopped (you can disengage the clutch, engage the gear and gently release the clutch pedal), turn out the spark plugs, make sure they are really installed by mistake, and install new ones.
It happens, however, that the spark plugs are not to blame, and the engine runs unstably at a high crankshaft speed with all signs of glow ignition. This happens when a significant layer of soot has formed on the bottoms of the pistons and the surfaces of the combustion chambers. The formation of soot is the result of using low-octane gasolines or running the engine for a long time with a rich mixture. To prevent this from happening, you need to use only AI-93 gasoline and monitor the adjustment of the carburetor. But in order to eliminate the malfunction that has arisen, that is, first of all, to destroy the soot, you will have to contact the service station, since not everyone can competently cope with the whole range of work on their own. It will be necessary to remove and reinstall the cylinder head, adjust the gaps between the levers and camshaft cams, set the ignition timing, adjust the tension (belt) appreciate the timing mechanism, fan belt. Although almost any car owner can perform each individual operation, a set of such operations and the need for certain tightening torques for a number of connections require skill.