Busted/failing crank sensor?

[Timbuick]

guys, my normally reliable GN took a sudden nose dive today under hard acceleration, accompanied by a back fire I also largely lost my idle, it became lumpy and fluctuated between 550-950rpm.
No adjustments to IAC/TPS managed to help, neither did changing the MAF.
I have had a chirruping sound from somewhere at the front of the motor and wondered if the crank sensor was coming into contact with something.
Any suggestions welcome

 

[azbob]

You have self diagnosed the potential problem. Inspect the crank sensor and realign/replace if necessary. I had a similar noise and the crank sensor was contacting the reluctor ring. Simple fix to adjust in my case.

 

[84BuickGNYorkPA]

Double check the crank pulley is tight.... been there before..... same symptoms.

Chuck