My 87 325is

Fuel filter, fuel pump relay, fuel pump. This year was a crossover from 2 pumps (1 external, 1 in tank) to 1 internal pump. Checking/changing these shouldn't take more than 2 hours tops. I'd also remove the fuel injectors and have them professionally cleaned and tested. Mine were done for $120 and made a WORLD of difference. If you can get the newer 3-pintle Bosch/Ford injectors cheap, do it. Just make sure the resistance is the same (Ohms). I have more info on injectors if you want it.

Bill in Omaha '86 535i

Thanks for the input. I've actually checked the fuel pump relay and in tank fuel pump. I replaced the fuel filter and fuel pump due to buzzing, but the pump I got off my parts car buzzed just as much. I've had a few other opinions on it and they all seemed to jump right to ignition. After checking almost the entire electrical system (minus the ECU), a problem with the injectors makes sense. We actually just rebuilt the head after a blown head gasket and I cleaned the injectors as well as I could. It had been running great for a couple months and just recently started stuttering. I'll definitely check the resistance on the injectors. Thanks!

Does "almost every sensor" include the cam position sensor?

There is a HUGE conversation -- hundreds of posts, i think -- on this topic on the bimmerforums site. It seems, unfortunately, that there is no single answer to what causes the all too common hesitation, and that trial and error of going through all sorts of attempted fixes can be quite expensive and time-consuming and frustrating. but have a look there for a list of dozens of things that others have tried/ tested/occasionally found to work. personally, i passed on a couple of e30's for sale because of this, and waited to buy (my new--to-me 85