The carburetors are set to constantly enrich the mixture, the oxygen sensor tells the computer the concentration of O2 in the exhaust gas. The computer then activates the EACV to add just the right 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 released from the combustion chamber is checked in order to regulate the composition of what enters it. Under certain conditions, such as manifolded throttle opening or warming up a cold engine, the computer is programmed to interrupt the feedback and go to open loop, i.e. ignoring the readings of the oxygen sensor and regulating the intake of air according to the programmed program. One of the conditions for the transition to an open cycle of regulation is sudden rapid inhibition. On an engine with a carburetor, a sudden increase in manifold vacuum causes an enrichment of the air-fuel mixture, the so-called. "release", which can cause backfire in the exhaust system and damage the catalytic converter. To prevent this, the computer will follow the airstroke control program and open the EACV as much as possible. A strong blow of air will have to be on the intake manifold to eliminate "ejection" enriched air-fuel mixture. This program does not start at low speeds or when the coolant temperature is low.
Air Retardation is another open circuit program that is activated when the engine is rapidly decelerating. It runs much the same processes as an airstrike program, but will maintain a slight air/fuel ratio variation for optimum emission performance. Hot Start Control is another air/fuel mixture program designed to help start the engine more easily when the coolant temperature is high.
These systems operate on a combination of vacuum and electrical signals. They are extremely prone to malfunction due to faulty vacuum connections. If the vacuum is not applied to the component in time, it cannot work when it is needed. When working, pay special attention to the connection and placement of each hose.
As systems become more complex, the number of vacuum hoses in them increases to such an extent that the complexity resembles automobile maps of large cities. Even the hose numbering used on the latest models does not prevent erroneous hose connections. Be constantly attentive.