I have an 87 420 SEL in which the engine has been shutting off while I am either sitting at a light idling or when I am coasting down a hill and not pressing on the accelerator. I suspected my fuel pump relay and jumped the pins that keep the relay running when the ignition is turned on but the engine continues to shut down intermittently. I also suspect maybe a low idle was causing the problem so I disconnected the idle control valve which increased the idle about 750 more rpm but the engine again died while coasting down a hill yesterday. I replaced the fuel filter about three years ago so I don’t suspect it’s the filter and the fact the engine simply dies instead of sputtering before it dies makes me think its not fuel delivery that is source of the problem. Usually the engine starts up again as if nothing is wrong, yet a few days ago, for the first time, I did have to crank the engine several times to get it restarted. I live in San Francisco and driving around this town with the possibility of loosing my power brakes while going downhill adds a whole new element to city driving. Any suggestion on where to troubleshoot would be appreciated.