Hi Everyone,
I'm working on a friend's 1998 XJ8 with a 4.0L naturally aspirated. My problem is that the car will make a fairly loud rattling/humming noise near the throttle body. Does anyone have any idea what it could be? I think it could be the throttle body motor, but I don't understand it's operation. I think I read somewhere that it's the cruise control motor. Any ideas? It sounds like a timing chain rattle, but I don't understand why it would be coming from the back of the engine, not the front.

Thanks in advance.

 

Now that I listen to it more, it sounds more like a whine that changes with engine speed. It's definitely engine related because it will do it parked or in neutral. If I didn't know it was coming from the area around the throttle body, I would have said it was low on power steering fluid. It doesn't really whine much at idle but once you touch the gas, you can hear it. Any one?

 

Could it be the torque converter?

 

I suppose it could, but I don't know what a failing torque converter sounds like and would it make a whining noise? It does change pitch during the shifting process. The pitch increases until it reaches shift speed then the pitch drops once it's shifted.

Logically, it makes some sense. I was thinking it might be the transmission input pump, which is right there with the torque converter.

 

We're both just guessing. You could always take it to a transmission shop, but would you believe what they say?