Hey all, I have a problem mwith my 2002 ZR2 Blazer. the service engine soon light won't shut off. I have tried to reset the computer by disconnecting the battery, that didn't work . I went to autozone to run the codes to find out what the problem was. the codes came back as a small evap leak and a bad cam sensor. So i replaced the sensor and cap and still have the same problem. Now i have a loud tapping noise when i start the car especially when its cold out. I DON'T KNOW WHAT ELSE TO DO? Any help would be appreciated.Is it possible that the emissions system needs to be checked out? thanks Scott

 

Everyone on here is going to ask for the specific codes, that is where you need to start...

Once you have the codes then there is a wealth of information using the search function with the pXXXX code you pull from a scan tool.

 

What He Said!
And here's why...
That you say you replaced the cam sensor in such an offhand manner makes one wonder.. it's NOT JUST a matter of unbolting the old and bolting in new. Unless you really mean Crank Sensor.
The CAM sensor is what we used to call a Distributor. NOT a simple thing.

As to your knock when starting cold.. that's POSSIBLY a lube problem Could be a sticky lifter OR piston slap. It probably goes away as engine warms, right?
Question: Does it get LOUDER as you accelerate? Note I didnt say faster, said louder.

 

The crank position sensor has very thin shims that have to be replaced & it is a very easy swap. I think it's a 10mm bolt holding it in. You wouldn't hear the CKP sensor tapping/getting hit more than twice in the position it's in. It would just get the sensor head broken off & the engine would probably die or run like crap.