QuestionI have a 1999 Dodge Stratus with a 2.0L four cylinder. At low speeds, mainly idle speeds, it has a severe engine knock, almost as if the engine is being deprived of oil at low speeds. As the gas is slowly depressed, the knock almost completely disappears as the engine nears 1200 RPM. Any advice on what the problem may be. The car has 124,000. Thanks
AnswerWell, when it comes to noises it's sometimes difficult to compare noises based on just words alone. What I call a tap you may call a knock. What I call a click you may call a tick.
Point being that without hearing it I won't be able to tell you whether what I hear is what I'm about to describe. But here's a few problems I've run across working on that engine in that vehicle.
2.0L DOHC has slightly noisy lifters with higher mileage. These are frequently described as a ticking or clicking noise and will go away most of the time once you take it off of idle. The reason this happens is the lifters wear down and clearances increase. When you rev up the engine you increase oil pressure. The lifters in this car are hydraulic meaning... oil pressure makes them work. You increase RPM and you increase oil pressure thereby making the lifters work a bit better.
After the lifters there's a possibility that you've got a crack in the exhaust manifold. This happens mostly between cylinders 2 and 3 (dead center of the engine) Sometimes the ticking noise will be loudest when the engine is cold. As the metal heats up it will change dimensions a small amount and may make the noise stop or get exhibit itself.
The next possible noise on the list is the piston and rod assemblies. The pistons are made of Aluminum and silicon. Very light, durable up to a point and work well. The connecting rods are made of powdered steel. Again, strong and durable but the two different types of metals don't always expand and contract at the same rate. This causes noise in the engine bay when the engine is cold and really exhibits itself in cooler/winter weather. Most of the time this will go away after about 5-10 minutes of driving.
The last noise could be bearing damage in the bottom end of the engine. This sort of noise is not one to be ignored expect it to go away. An oil pressure gauage needs to be hooked up to the car in order to start the diagnostic procedures here and may or may not yeild immediate findings. Debris in the oil pan, the oil pick up or even just a simple low oil condition could be the cause of an oil pressure loss or engine noise.
If you've got anymore information you can lend me or need anymore from me just ask.
Doug
