Bad Pulley...Please HELP

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So I had a very loud, quick screeching noise as soon as I started engine, replaced ALL belts, lower engine intake hose then noise went away, now noise has returned and is more constant and when driving, it shakes and feels like it's going to stall with the check engine light blinking.....HELP I am a single mom, this is my only transportation and need someone 's advice so I don't get taken to the cleaner!!!