I have what sounds like an angry sewing machine in my engine... and the idle bounces about 150 rpms continously... anyone have a clue what this might be?

 

Its a 3.4l 2003 monte carlo

 

the good news is sounds liek you keep a good ear on your car.

but the bad news is it could be a bad liffter or some thing internal in the motor.

park the car on real level area. and let it stay there for a while to allow the oil to get back to the pan. check it. make sure that your up to par on that first.

if this is still not the issue you might see if you can get it to pull a code from like Auto zone etc...
If so see what happens on that .

my old car did this and i fould a colapsed liffter in it and it was causeing it to rattel .

 

Well, it has thrown a check engine code.. but i am afraid to drive it to autozone in fear that i will make something worse (autozone is about 1.5 miles form my house.)

I bought the car off a friend who recently had a backyard mechanic replace the intake manifold gasket and it started making this noise about 3 miles after he got it back from the mechanic.. not sure if any of this info helps.