Car began to misfire under load once warm, replaced plugs and wires which wires were bad. Dist replaced appx. 1 year ago. Did not fix problem. I unhooked battery and let sit awhile then rehooked and ran perfect for about a month (I drive 100miles daily). Now it has began ti start again it begins near the end of my 50 mile drive and becomes sooner as time progresses. now about 10 miles in it starts and is alot worse. I unhooked negitive and that didnt fix it this time. Pulled plugs and the have black on them. injecters are ticking and sound normal. I haven't located any vacume leaks. My guess is a senser or computer but don't know where to start and don't want to put alot of money into a $900 car. Please help. Thanks