Hey guys,

So after finishing the head gaskets and all the good stuff on the way down and back up, my blazer is running like crap. It ran good for about a month but now while driving my temp guage will go up to almost 125, then down to 45 and back to about 100. Whenever it does that the rpms drop/raise and that of course affects my speed. It's not consistent (*not once it warms up/high speeds, etc) and it has stalled out if I'm nopt pushing the gas, and once again, not consistently. Any ideas of what this would be?
I had my fuel pump replaced along with a whole whack of other stuff last year, with just a one year waranty on it all which is of course expired. And I do have a code, havent been able to check it yet though

Thanks