will not rev past idle

I have a 92 mighty max, ended up rear ending someone on the highway. the entire radiator support got pushed in pretty good. so I started digging into it got everything out of the way and fired it up. I ran it maybe a few minutes just to make sure it still ran. after shutting it off and coming back to it had 0 throttle response and would try and die. wondering if there's a limp mode sort of feature that these trucks have if their overheating? The coolant temp gauge didn't go past operating temp as I didn't want to warp the head. any other input would be helpful, Thanks