i had a hesitation problem with my 88 760 with the b280. you could restart it and a few times and it would go away, or sometimes it worked right on the first crank. i tried every sensor on the engine, engine grounds, and even took it to a volvo dealer to diagnose it. they said it was the intake manifold gaskets, which was a bunch of BS, i had already check those gaskets, and could clearly tell that the problem was one of an electrical nature since it was not temperature dependent. last week the car stopped running altogether, and although i was upset, i was also relieved in a way, because now i figured i could troubleshoot the problem and see what was wrong. after checking the car out for a little bit i verfied that there was spark, but i noticed i couldn't hear the main fuel pump running, so i changed the fuel pump relay with a known good one. no go. still wouldn't run. so i got down under the car and checked for voltage at the pump, which it had, however the pump only made a slight whirring sound. i came to the conclusion that the pump needed to be replaced, and after i changed it, not only did the car start, but the hesitation problem is completely gone. i'm sure having new sensors all over the engine didn't hurt any, but they certainly didn't do anything to correct the problem prior to changing the fuel pump. i hope this helps some people, cause it really drove me nuts.