you have hit the nail on the head this is temp related.now is there any diff in the engine temp gauge when this occurs?does the temp usually stay at 85 and now it's going to say 95 or 100?this is one of the early 119 engines that suffered from the "green crud" remove both of the distrib caps and look to see if you have the green crud disease both on cap and rotor buttons.pull a couple of plugs at random and look for anything unusual.do you run the climate control all the time?does the a/c begin to load up at the temps you describe?because if true then it may be nothing more than vac leak.send some answers and maybe i can help. david poole european performance dallas tx.