Introduction and MAP Sensors
All delayed replica cars are fuel injected. They are solely dependent on sensors to supply the necessary information to the on board computer to properly deploy the proper engine management. For information as to the amount of air flow into the engine, the computer utilizes either a MAP sensor or a mass air flow sensor. The MAP sensor operates off of the vacuum from the intake manifold of the engine to determine height above sea level for atmospheric pressure and engine demand. The Mass air flow sensor works on a different principal to arrive at the same result. It utilizes a small wire in the intake air passage that is attached to a small circuit board. The computer sends voltage to this wire to heat it to a specific heat range. The air passing the wire cools the wire and the computer will sense the temperature drop through the circuit board and increase the power to the wire to keep it at a constant temperature. This constant voltage change, in an effort to maintain a certain temperature, is used by the computer in conjunction with input from other sensors to manage fuel and ignition timing.
Cracked Vacuum Hoses
Cracked vacuum hoses create an air leak that is not metered by the computers systems. When unmetered air is introduced into the system, the computer sees this as an extremely lean condition. Some cars will not even run or will barely run with cracked hoses.
ConclusionOn older carbureted cars, it takes vacuum from the engine to suck fuel out of the carburetor. This will further cause a necessary increase in timing to burn the extra fuel.
Vacuum Leaks and Idle Functions
At an idle, the idle air motor will not operate properly. The idle settings will deteriorate. Upon accelerating, the computer has already made adjustments to correct for the lean condition by increasing timing and by further increasing it would fall out of parameters. The effects of cracked vacuum hoses on a fuel injected engine have only been covered in a small part here. There are a lot more far reaching problems then just these that could be discussed. This means that there is too much air and not enough fuel. The computer arrives at this conclusion when it monitors the free oxygen sensors. The oxygen sensors' signal is generated by free oxygen passing over the sensor and indicates whether the mixture is to lean or rich to produce the desirable 14.5 to 1 mixture. The computer in turn will try to enrich the mixture to prevent a lean mixture.
Create an air leak as in a cracked vacuum line that reduces the vacuum at the carburetor to suck in fuel and a lean, unmanageable condition exists. Too much air and not enough gas equals lean, which in turn equals no power.