The carburetors are set to constantly enrich the mixture, the oxygen sensor reports the O2 concentration in the exhaust gas to the computer. The computer then turns on the EACV to add the required amount of air to the intake manifold to maintain the ideal air-fuel ratio in the air-fuel mixture under all engine operating conditions. This is the feedback loop: what is leaving the combustion chamber is monitored in order to regulate the composition of what is entering it. Under certain conditions, such as the manifold throttle opening or warming up a cold engine, the computer is programmed to interrupt the feedback and go into open loop, i.e. ignoring the readings of the oxygen sensor and regulating the air intake according to the programmed program. One of the conditions for the transition to open loop regulation is sudden rapid braking. On a carburetor engine, a sudden increase in manifold vacuum causes the air-fuel mixture to become richer, the so-called "blow-by", which can cause backfire in the exhaust system and damage the catalytic converter. To prevent this, the computer will follow the air shock control program and open the EACV as much as possible. A strong air shock will be applied to the intake manifold to eliminate the "spill" of the rich air/fuel mixture. This program will not be activated at low speeds or at low coolant temperatures.
Air Slowdown is another open loop program that is activated when the engine speed is rapidly reduced. It runs much the same process as the Air Slowdown program, but will maintain a slight deviation in the air/fuel ratio for optimum emissions performance. Hot Start Control is another program that varies the air/fuel ratio, designed to help the engine start more easily at high coolant temperatures.
These systems operate on a combination of vacuum and electrical signals. They are extremely prone to failure due to faulty vacuum connections. If a component is not supplied with vacuum in time, it will not operate when needed. Pay particular attention to the connection and placement of each hose when working.
As systems become more complex, the number of vacuum hoses in them increases to such an extent that their complexity resembles that of road maps of large cities. Even the numbering of hoses used on the latest models does not save from erroneous hose connections. Be careful at all times.
[Article source on the website HONDABOOK.ru]