I'm trying to help out a buddy of mine who has a 92 K5 Blazer TBI. Here goes. When you first start it in the morning it will idle really rough and gives off a SES light, then the temp climbs to the red really fast. After seeing it overheat so quickly I shut it off and noticed the coolant was boiling in the upper radiator hose.

From the little reading I've done I think it might be the coolant temp sensor and/or the thermostat.
I'm going to replace both of these tomorrow but I'm not too familiar with these engines so I'm not sure if it's not a cracked head or bad head gasket maybe?

I can't see any evidence of the coolant or oil mixing. Just the terrible loping/surging idle for about ten minutes then it'll stall out.
I turned up the throttle cable and started it back up and it overheated within a minute. Any ideas?

Cheers!

 

Have you checked the plugs or done a compression/leakdown test? You may have a head gasket problem.

 

Is it possible it's just the temp sensor and maybe the thermostat causing it to heat up so quickly?

 

I have a 92 Blazer that has never failed me. It will not start now. It is not getting fuel to injectors so I have rebuilt top half of throttle body ,replaced fuel filter,replaced injectors, tested electrical connectors with noid light and getting strong pulse. Checked fuel pump it is working and I am getting fuel to the throttle body but fuel not coming out of injectors. Please Help