When the car is idle it makes a loud noise,also it revs like 1500 and accelerates on its own. Any suggestions on what you think the problem could be?
Make, model, year, miles, auto/manual?
Aw, c’mon edb it’s a 94, do you really need specifics 
When the car is idle it makes a loud noisethat's how you know it's running
it revs like 1500idles too high
accelerates on its ownneed to actually push on the brake
Look for a vacuum leak.
Clean the throttle body and IACV.
There are cars out there with carburetors (still), cars with throttle body injection, cars with port injection, cars with direct injection, and even cars with combination of port injection and direct inject (FRS and BRZ).
The area naturally aspirated cars, turbocharged cars, and even supercharged cars.
There are air pumps out there (still), cars with EGR systems and cars without EGR systems. There are 4 cylinder engines, V6 engines, straight 6 engines, V8 engines, horizontally opposed engines, even V10 and V12 engines.
There are cars with distributor based ignitions with points (still), cars with distributor based systems without points, systems with Coil-On-Plug systems.
There are cars that haven’t had a tuneup in 200,000 miles and cars that get new plugs every 50,000 miles.
And, finally, there are old cars, medium age cars, and new cars.
Man, we’re happy to help, but you have GOT to narrow this down so we know what we’re helping to troubleshoot. You’ve given us no place to start.
I apologize I thought I had the specs in the description. Its a 94 Mercury Cougar 3.8.
A noise could be a bang, knock, whine, hiss, or a banshee wailing…so what kind of noise is it?
Offhand, the revving sounds like an Idle Air Control Valve gone stupid if you mean that it does this on its own while sitting and idling in park or neutral.
If the noise mentioned is a hiss then any vacuum leak will have an effect on the IAC valve.
probably a vacuum leak
The noise is more like a loud humming. I’ve checked for vacuum leaks but didn’t find anything
The symptoms are text book indications of a vacuum leak.Of course the idle air control is a regulated vacuum leak and if it hangs open it is no longer regulated.
Fords are notorious for making a humming sound due to IAC motor failing. This noise could also be caused by a dirty air filter.
You have my sincere apology for not having read the thread title. Allow me to plead old age… On my computer, when I scroll down to the narrative the title disappears. {
Having started with such an embarrassing mistake, I’ll leave the rest to the others here.
you did notice there are 5 agrees with an earlier post I hope?
I had 3 cougars of your type, I wish I could help but ours never broke down.
sounds like you have a minor problem, hopefully