I just finished doing head gaskets on my 91 Toyota 4Runner. I'm having a problem with it overheating when I put a load on it. Like accelerating up a hill. It also seem to have a little miss to it . I just pulled the timing cover back off and my marks line up. I put new plug wires on. The water pump I replaced about 8 months ago.Any ideas as to why I'm over heating ?

I would look at the radiator being plugged, or thermostat hanging up..

I took the thermostat out , 2 weeks ago I was driving it with no heating problems . I triple checked the gaskets before I put them on . It just blew a head gasket , the temp never got to hot to warp anything. I checked them with a straight edge.

I watched the water flow with the cap off , It seemed to move ok . The fan is on correctly.

No the heating problem did not go away when I removed the thermostat

backflush your cooling system,run water backwards through your system in case anything has hung up in your heater core,and flush your radiator as well forwards and backwards

make sure you burp your cooling system as well

your thermostat has a little hole on the side of it that hole needs to be on the top when you install it ,its an air vent