How to diagnose cold engine noises
So I decided to diagnose my engine noises and I would like to share what I found. First, I bought an auto stethoscope. For those that are unfamiliar with these they look like a medical stethoscope, except that they have a metal probe sticking out from the part that your doctor normally puts on your chest. These are great devices for locating engine noise, including piston slap. They are inexpensive. I paid $20 from my local NAPA store, but they can be had for under $10 on the web.
Next, I took off the plastic valve cove shrouds and started my car. I noticed that my engine sounded somewhat quieter. This surprised me. However, I could still hear quite a bit of noise. I probed the valve covers and the block with the stethoscope to locate the engine noise. Everything sounded fine. Finally I put the probe on a fuel rail and a fuel injector and wow are they noisy! I have never heard anything that loud from any other fuel injected car that I have owned!
So my engines noise is coming from my fuel injectors. When I reinstalled the plastic valve cover shrouds the noise seems much louder! I think the plastic shrouds amplify the noise because they cover the injectors and partially snap on the fuel rails! I feel much relieved since this is normal noise. I highly recommend purchasing one of these stethoscopes. They really work!






