If the battery terminals are clean and tight, then the next item to check is drive belt tension. If the belt which drives the alternator is too loose, then the alternator will not produce enough electrical current to keep up with demand. Many modern vehicles utilize a single belt which drives the alternator and other accessories. This system usually also has an automatic belt tensioner which always maintains correct tension and is not adjustable. If your vehicle uses a wide, multigrooved or so-called "Serpentine" belt to drive the alternator, then it likely also has an automatic tensioning device.
A dirty or clogged engine air filter is more likely to reduce acceleration than fuel economy, according to tests conducted by the EPA. Because filters get dirty gradually over time, you might not notice a small but steady loss of performance until your car is accelerating like a turtle. But if you haven’t changed the filter in a couple of years (or sooner in areas that have a lot of soot in the air), that could be part of the problem.
These can often be difficult to bolts to remove. You may need to use a ratchet with a long extension to provide the necessary angle to access and turn the bolts. Pull the motor and harness out as one assembly. Once you have the assembly removed, you can separate the two pieces and replace the one that is malfunctioning. Re-install the motorregulator assembly. Once you have replaced the malfunctioning part, whether it was the motor or the regulator, it is time to slide the assembly back into the door's interior and bolt it back into it's original position.
When to Change Your Car's Battery. There are several signs that indicate the battery in your car is failing and needs to be replaced. Sluggish engine cranking and unusual electrical problems like flickering headlights are telltale signs of trouble, though they may also indicate problems with your car's alternator. You should also replace your battery if it is bulging or has a rotten egg smell.