Volvo: starting problem, mass air flow sensor, mass air flow

Question
where do i start? ok i have a 91 volvo 740. And about a month ago i noticed the engine was running funny...but everything was ok....so i was at a friends house one night and on the way up there it kinda felt like my engine was bucking a little bit but not so much. So when i went to go and leave it wouldn't start yp. The next day my dad came up to look at my car he tried to start it 3 times and on the 3rd time it started up and was running fine. about a week after that i noticed that my idle time would drop everytime i stopped(i would have to keep one foot on the gas the other on the break so it wouldn't stall) so now when i try and start it all of the lights, windows and radio work but it just won't turn over.We have changed the ditributor, and rodar cap. we also replaced the coil . we are at a loss on what could be wrong with it and how to fix it! (we also checked the fuel line and whatnot and that was fine) Can you please help me on what it could be and how to fix it?
Thank you so much
Nicole

Answer
Nicole,
Preform these test and lets see what they show. Is the fuel pump in the tank running? Is the main pump running? If they are what is the fuel pressure? It should be about 42 psi. Make sure that the fuel filter is not blocked. Check for spark. Check for a pulse at the injectors (use a noid test light).
If you have no spark see that all the wires are on the coil and that they are tight... Check to see that there is power to the coil. The blue wire 12 volts key on the red wire/or brown 12 volts pulsing on /off while cranking.
No fuel make sure that the fuse and relay are working. Power to the pump and still no gas, pump is bad.
No pulse at the injectors, radio suppression relay,power stage or the LH control unit.
Check for codes in the LH sysem and also the EZK system, they maight give you an idea what and where to look. Mass air flow sensor and the flywheel pick-up have large failure rates.