Modern cars run off of electronics – and electronics run everything, so having a poor quality electrical system can be detrimental to the system in a number of ways, but here are the top 3.
 
ECU
 How the ECU gets information from the sensors is via electrical signals, or in other words, voltage. When you have a poor electrical system, sensors may not be able to output the correct voltages based on what it should be seeing and reporting to the ECU.
 
Injectors
Fuel injectors are essentially solenoids that open and close when voltage is applied and removed respectively. The injectors have a minimum time from when the pulse is sent to when the solenoid starts to open. This is called the “Dead time”. Different injectors will have different timings, but system voltage can impact the dead time, causing it take longer to start to open and reach minimum flow.
 
Coil packs produce high voltage from a low voltage supply, usually generating 40,000 volts or more. This voltage is what travels through the spark plug and causes the spark that ignites the air/fuel mixture in the cylinders.
 
Ignition 
As with the fuel injector, there are things that need to happen with the coil in a certain amount of time. The most important is the dwell. The coil pack has to charge up its energy and that can take some time. System voltage can impact the dwell time and if it takes too long, the coil will release its energy before it has reached its maximum strength. Depending on how long it had to charge up, it can shorten the duration of the spark, or worse yet may not be enough to cause a spark across the spark plug gap at all.