I have a 1994 Blazer Tahoe edition 4x4. Can someone tell me how to go about replacing the fuel injector.

Also, the four wheel drive will not lock in in the front, could it be an electrical problem? Any advice?

 

If CPI, you have to pull the upper plenum off the engine. Check out the CPI FPR replacement thread in the Tech Article (DIY) section (index link in my signature). While you are in that section, check out the 4wd related threads.

What is your truck doing that makes you think you need to replace the injection system? If you do go through with the replacement of the injection spider, don't forget to replace the internal lines as well. They like to leak after being disturbed.

 

It idles rough and at its worst it wants to cut off everytime you come to a stop. I have to push on the gas and break at the same time to keep it from cutting off or put it in neutral. The braking system is also really hard to use when it does this.
Sometimes putting fuel injector cleaner and using high test gas helps.

I was advised to clean the throttle body but haven't tried that yet. Do you think that would solve the problem?

 

Before condemning the spider, you really need to test the fuel pressure & leak down with a fuel pressure gauge connected to the port on the back of the intake near the brake booster. You should get >55psi with the pump running, engine off, and it should remain above 50psi for 10 minutes after the pump shuts off.

From your symptoms, you could have a fuel system problem, but it could be some other things. A dirty/clogged EGR (exhaust gas recirculation) valve for instance. It is relatively cheap & easy to pull off the EGR valve & clean it. Install it with a new gasket. They make a gasket with an integrated screen which can keep larger chunks of carbon from getting stuck in the EGR valve.

As far as cleaning the throttle body, it wouldn't hurt to do it. A dirty/sticking IAC (idle air control) valve can cause those symptoms as well. The IAC valve is mounted in the throttle body and will need to be removed in order to clean it.

 

‪Vortec Chevy Problem and Fix!‬‏ - YouTube

Thats on how to change the regulator/injection system if its bad.