Mitsubishi Repair: 98 Galant Viento, 1.8, automatic, firing order, speed sensor

Question
When coming to a halt and at times while at idle the engine check light comes on, the car's idle gets rough as though it will shut off and in fact shuts off at times. Restarting the car is no problem and while driving the vehicle performs great. I did a diagnostic test and was told that the speed sensor by the throttle body and the ignition coils are failing. Can the failure of the ignition coils cause the problems I am experiencing?

Answer
Neil,
Yes, a malfunctioning ignition coil can cause this problem.  When the ignition coil stops working as it should, your spark plug firing order and timing can get thrown off.  This will causing rough idle, stumbling and stalls.  

The speed sensor should also be inspected to determine if it really is failing.  Get your alternator tested as well.
Good luck!