Reader Question: I have a 2001 Jeep Cherokee with about 88,000 miles. I have had it now for a few years. It is making an annoying high-pitched tone sound. It happens when I drive it for a few minutes going around 55 MPH and then I let off the gas pedal.
As soon as I lift my foot off the pedal, I hear a high-pitched tone coming from under the hood toward the driver’s side. I know that it is coming from under the hood because I can stop the Jeep and it is louder under the hood than in the passenger compartment. When I do stop and try to find where the sound is coming from it will stop in only about 1 minute.
Even if I rev up the engine while in park and try to get it going again, it does not happen. To get it started back I have to drive it again up over like 50 MPH. The sound only happens when I take my foot off the gas pedal.
If I push the pedal down while it is making the sound, the sound stops, and as soon as I take my foot off the pedal, again it will start. Therefore, you can make it sound like, hummm stop humm, stop, hum, etc. I have had mechanics look at it and no one can figure out what it is. Most say it sounds like some sort of air leak. Please help me!
This is a new one on me, and sounds frustrating as heck! The air leak MIGHT be a good place to start your investigation. I would have your mechanic start at the air cleaner box where the air cleaner is, sometimes the mechanics put the air cleaner box on wrong when the change the air filters.
Make your way from the air cleaner box to the engine, looking and feeling underneath the plastic hose connecting the air cleaner to the engine. Make sure there is not a hole on the underside of the air cleaner hose that would cause an air leak.
Lastly, get your mechanic to inspect and CLEAN the throttle body. He can use some intake cleaner to spray around the throttle body with the engine running to find a vacuum leak there.
I have seen a dirty throttle body cause a vibration and a noise at idle, it could be what is happening in your situation. Cleaning the throttle body should be done periodically as maintenance anyway. Therefore, it will not hurt anything to have it inspected and cleaned.