Random car maintenance question

[brewer12345]

My subaru has started making a rhythmic rattling sound from the engine when I am at highway speeds cruising on a flat stretch of highway. If I give it a little more gas or let up on the gas, it goes away. I heard the same thing from my old escort. What is this? STP (stuff in the red bottle)seemed to help with this in the escort.

[cube_rat]

Quote:

Originally Posted by brewer12345 My subaru has started making a rhythmic rattling sound from the engine when I am at highway speeds cruising on a flat stretch of highway.* If I give it a little more gas or let up on the gas, it goes away.* I heard the same thing from my old escort.* What is this?* STP (stuff in the red bottle)seemed to help with this in the escort.

Dirty gas. Have you been using 87 octane?

[brewer12345]

Yup, I use the regular stuff. Doesn't seem to make a difference whether I use name brand stuff or noname.

[OldAgePensioner]

Sounds like timing. If the ignition in the cyclinders takes place at the wrong time in the compression cycle it can cause a sound like someone tapping very lightly with a hammer on the engine.

When you speed up or slow down, the timing will either advance or retard and that will stop the pinging.

PS: One question is when at steady throttle does the car seem to surge/slow just slightly. A worn timing belt can cause that.

[brewer12345]

Quote:

Originally Posted by OldAgePensioner Sounds like timing. If the ignition in the cyclinders takes place at the wrong time in the compression cycle it can cause a sound like someone tapping very lightly with a hammer on the engine. When you speed up or slow down, the timing will either advance or retard and that will stop the pinging. PS: One question is when at steady throttle does the car seem to surge/slow just slightly.* A worn timing belt can cause that.

NNo surging or slowing at idle. Engine seems perfectly normal except for when I am at light load cruising. Its only got 44k, so I can't imagine the timing belt would be worn yet.

[F M All]

Quote:

Originally Posted by brewer12345 My subaru has started making a rhythmic rattling sound from the engine when I am at highway speeds cruising on a flat stretch of highway.* If I give it a little more gas or let up on the gas, it goes away.* I heard the same thing from my old escort.* What is this?* STP (stuff in the red bottle)seemed to help with this in the escort.

Last I heard Click and Clack were not FIRE. Try calling them, you'll get a laugh if not a solution.

[yakers]

I would normally avoid higher octane gas but in this case I suggest trying a couple tankfulls. As cars add miles they can build up a carbon deposit and require a bit more octane. So its a cheap thing to try, although what is usually noticed is at acceleration rather than cruising. Checking the timing is a good idea too. I have a new car 05 Ford Focus and I can tell slight power shifts when I do not expect them. In this case I think it is the emmisions computer making adjustments. Something I just have to live with.
It depends on how many miles you have too. Things like oxygen sensors flake out. But try the cheap stuff first.

[Dreamer]

That would be my suggestion also- call Car Talk on NPR. They are on Saturdays at 10:00. I do not know anything about cars and don't really want to know anything about fixing cars, but the Tap It brothers make me laugh!!! There laughter is contagious!

Dreamer