A Brief Auto Repair Q & A

February 1st, 2016
At BCS Tires & Lifts in College Station, TX, we sometimes run across customers who have questions about certain aspects of auto repair. We’d like to answer a few of those questions if possible: 
Q: What exactly is the ECU? 
A: ECU stands for Engine Control Unit; it’s also sometimes referred to as the Powertrain Control Module, Engine Control Module or just the “engine computer.” The ECU regulates just about everything pertaining to the engine. It takes information from a number of different sensor systems on the engine and in the exhaust stream, controlling ignition timing, air/fuel metering, idle speed, valve timing, transmission shift points and other functions. Emissions, fuel economy and power are controlled by the ECU. 
Q: What controlled these functions before the ECU was introduced? 
A: On older vehicles, a mechanical carburetor was responsible for fuel metering, while the engine’s distributor took care of ignition and spark advance. The distributor’s spark control was operated by vacuum from the engine and could change the spark’s advance curve according to load or acceleration. These systems tended to be much more maintenance-intensive than an electronic ECU. 
Q: Why is my Check Engine light on? 
A: The Check Engine Light, also referred to as the MIL (Malfunction Indicator Lamp), is designed to inform you of a problem that’s been registered in the ECU. When one of the chain of sensors that informs the ECU is sending a reading that’s outside of normal parameters, it registers a trouble code in the ECU’s processor and illuminates the MIL. A tech can then connect a diagnostic code reader to the ECU’s diagnostic port and access the trouble codes stored in the computer. NOTE: a flashing MIL is an indicator of a serious problem! 
Q: When should I have my timing belt replaced? 
A: Firstly, let’s discuss what the timing belt does. The timing belt is what enables the engine’s crankshaft and the valves to work in conjunction with each other, opening and closing the intake and exhaust valves in the combustion cycle. Many are still designed with a timing chain; this bicycle-style chain connects the crankshaft and camshaft and will last for the lifetime of the vehicle. The timing belt, however, is a toothed rubber belt that will stretch and eventually break. Most vehicles require a timing belt change between 50-100,000 miles (check owner’s manual). 
Q: What happens if the timing belt breaks? 
A: In many cases, once the pistons and valves fall out of sync with each other, the pistons will travel upward in the cylinders and crash into opened valves. This will bend the valves, possibly punch holes through the pistons and essentially wreck the engine. Some engines are designed to prevent this, but many aren’t. That’s why it’s important to not postpone a timing belt change!
Q: What’s the “serpentine belt?
A: Up until the mid 90s, engine accessories like the alternator, power steering pump and air conditioning compressor were all driven by separate belts. This mean that the belts had to be offset from each other, taking up more space in the engine compartment. A serpentine belt runs all the accessories at once with a single belt, for more space efficiency and less drag on the engine. The serpentine belt is held to a regular tension with a tension roller; its one main disadvantage is that a broken serpentine belt means a completely shut-down engine, as none of those systems can work without it. 
There’s a lot to know about any vehicle, and we’re sure this didn’t answer all your questions. We hope, though, that it might clear up a few mysteries. If you’ve got any more things we can help you out with, give us a call and make an appointment with BCS Tires & Lifts in College Station, TX and we’ll be happy to help you out !
  Posted in: Auto Repair 101