1998 Buick Century SERVICE ENGINE LIGHT

Engine Performance problem
1998 Buick Century 6 cyl Automatic 125000 miles

Hello,

My service engine light keeps coming on after i feel a small jerk!
Took it to auto zone code read crankshaft sensor...Replaced sensor code reset,drove for about an hour light came back on...

I took car back to auto zone code still came up crank shaft sensor..

I have a new mechanic i've taken it too..He put the car on the computer now its saying camshaft sensor...He replaced that sensor,full tune up,serpentine belt was squealing replaced the belt..
He reset code,light stayed off all Friday,till Saturday car jerked,light came back on...He placed on computer again crank shaft code again,he replaced ignition module,reset code couple hours later engine light back on...Gas miles not good when light comes on,car seems to stall going up hills before engine warms...Also heating control on operates on full blast,
no low setting must be turned all the way up to high just thought i throw this in as a side note might be related...

yesterday check engine light blinked for a second,blinked again and then came on..

I do hope you can help the guy isn't charging me more he just tells me to bring the car back to trouble shoot...Very good guy...Also the car light did go out right before inspection and car was able to pass...I'm clueless can you tell what this light is that's killing my gas miledge...

Thank you,