: Noisy Northstar

07-18-05, 08:24 AM
My 99 sometimes gets noisy. It happens around 1500rpm with a slight load on it. If I accelerate or decelerate it goes away. I am thinking spark knock but it is pretty loud. If I had mechanical trouble inside I would think it would be noisy all the time. What do you think?

07-18-05, 11:44 AM
What kind of noise is it? A tap, a clunk, a knock? Different sounds come from differrent components in the engine at different temps and speeds. You've got to be a little more specific. See if you can tell exactly what type of noise it is first.

07-18-05, 09:06 PM
It's like a knock, pretty loud for a spark knock. It usually happens with a light load on the engine. Are these engines prone to spark knock? Anyone else have spark knock?

07-18-05, 09:25 PM
Do you notice it when the engine is cold just after first starting it while it is warming up?? Is it just when you are in park/neutral revving it up to listen to it..??

If so it may simply be carbon in the combustion chambers. If you search using "cold carbon rap" and read up it might explain it.

Try doing some WOT accels to clean the carbon out of the combustion chambers and see if the noise disappears.

STS 310
07-21-05, 08:36 PM
Yea WOT. Plenty of WOT.

Run it like you stole it. (properly maintained of course).