my car starts rough, idles pretty bad, smells like gas, and a jingle can be heard coming from the back of the car at start up. once it gets down to 750, i hear a slight knock or ping which co-incides with a putt in the exaust. There is also a black film covering the inside of my tailpipes. check engine light stays on, flashes at 30mph without fail (however intakeparts have been thrown on)anyways all this Scares teh crap outta me whats up guys...

 

Flashing light usually indicates misfires. Get the car scanned & see what codes it is throwing.

 

I agree with Pete, sounds like a misfire to me, i had all the same symptoms when my car was misfiring...except all the weird noises...

 

The weird noises may be caused by the engine is shaking due to mifire.