3. Engine – Knocking and Compression
When the mechanic fires up the engine, he’s checking to see if it idles smoothly, and then if there’s any rattling or knocking while the engine warms up. These can hint at several problems including sensor issues, or worse, engine problems.
Knocking could also hint at poor care from the past owner, perhaps using the wrong fuel type, or abusing the engine.
A compression test is an important and easy way to see if there’s anything wrong. Using a small tool inserted into where the spark plug normally goes, one crank of the engine will reveal if the pressure in the cylinder is ideal. If it’s not, then forget everything else. This car isn’t for you.