95 explorer has very rough idle, back smoke coming from exhaust, bad smell of unburnt fuel, check engine light stays on---even after battery was removed for 3 days...i cannot read obd1 codes with scanner because i get a no comm at dcl message. Any info would be helpful! was wondering if the pcm may need to be replaced? Also, put in new plugs and wires last week, and the coil pack checks out.