My 2001 dodge intrepid has a loud knocking noise on startup. After its started it has a light rocking noise that gets louder when it idles at certain rpms around 1500 and 2000.
Could be engine bearings, valve timing components or just some drive belt accessory on the fritz. This is something where the expertise of an experienced shop mechanic is critical to getting a good diagnosis. I presume you’ve checked the engine oil level right? Next step would be to check the oil pressure using a shop oil pressure gauge.
Time to go car shopping.
As soon as I read this I wondered when was the last time I saw an Intrepid? The vast majority have already grenaded due to normal consumer abuses… Abuses that other vehicles are able to sustain far better it seems.
What you are describing is indeed big end bearing knock… Its curtains, unless you have a strong attachment to this vehicle it is time for a new car. Sorry.