Temperature gauge problem, and engine cuts out!

Hello, i'm having another problem with my blazer. Its a 99 blazer ls. Few months ago, the temp gauge would jump around and stay off randomly, when gauge was off, the engine would cut out. I was getting code for coolant sensor, so changed. It ran good for 2 days, then started up again. I went to take to garage couple days later and it quit, it didn't do it for about 3 months. Well the other day it started again. Someone told me it could be the temperature switch. The engine in this is out of 2000 astro van. Where would I find the temperature switch?? I can't locate it, or is this even the problem. Any suggestions please? I'm getting code for 2ndary air inject also, and random misfire, which i'm assuming is the plugs? did complete tuneup about a year ago. Thanks in advance

When you did your tune up did you replace the Distributor Cap? If so did you buy AC Delco? Random Misfire P0300 code can be Plugs, Wires, Cap, Rotor, or Coil. If You used anything other than an AC Delco Cap and Rotor, it is probably at least part of your problem. I would suggest replacing the Distributor cap and Rotor first, erase all of the codes and see what comes back. I know this doesn't necessarily address all of your issues, but it might work for you. I won't go into all of the juicy details, but I had a similar experience. Post back your results.

See this thread:
http://www.automotiveforums.com/vbulletin/showthread.php?t=975186

I do know that these ICM's are common on many other GM's including the LT1 motor. when temps get high, they cut out. the engine will turn over, but not crank until it cools off. then it will run fine, until it gets too hot again and kill the motor. some places can test it, but make sure it is HOT when you take it in. i let mine sit on the dash with the defrost on high heat to keep it hot til i got to the store to test it.

also, try an external temp gauge to make sure you are getting accurate readings