1992 Mercury Cougar is running rough and has a bad miss

we have a bad miss. new plugs, cap, rotor and tested plug wires seems to be all the same


Answer:

Well the first thing we need to do is determine what cylinder is causing the issue. With the engine running, ( EXTREME CAUTION : You will get shocked if you do not use protective gloves 15,000 volts )  remove one plug wire at a time and see which one you remove and the engine sound doesn't change. You have now narrowed the issue to one cylinder. check compression with a compression tester. Check for spark, check plug wires to make sure it isn't sparking through the boot. check for injector pulse. repair as needed.   If no one individual cylinder shows a difference , perform a compression test on all cylinders all should be with in 20 psi of each other.  If it fails , you have a blown head gasket. If they all pass the test then you may have a clogged EGR Valve or Clogged catalytic convertor.   Test each part and replace as needed.  Feel free to check out some of the other resources on the website as there may be some helpful information available.