Pontiac Repair: 1991 BONNIVILLE, ac delco, rod bearing

Question
QUESTION: Car is skipping really bad and the middle coil is not firing that good! I have changed the plugs,wires,coils,ignition mod, and the computer and still skips?!!! if you change the coils and rewire it the middle coil still doesn't fire correctly. motor only has 60,000 miles on it! thanks for your time!!!!

ANSWER: Hi James:

so the 2/5 coil is not firing? Is it dead or a sprratic misfire? if it's just one coil that you have issues with it can be a alot of things it can be an issue with either cylinder on that coil. If you start the car up with both wires off that coil and start the car up does the coil spark fin inbetween the coil towers? Don't run it for long that way because it really stresses the coil out but if the spark is blueish pink in color and constaant then the issue is not with the module or the coil. If the spark is not ther or is intermittant then it's an issue with the coil or the module or in input to the module. If the spark is good you need to look at a plug or wire issue I know you said you replaced them but the issue has to be there. Did you use AC Delco plug? ONLY USE original equipment plugs. How about a "GOOD" wire set like Delco or Bosch wires? in order for #2 or #5 to fire the opisite cyliner #5 or #2 has to be good the coil fires both cylinders at the same time it's a loop. so one can effect the other. good luck :)


---------- FOLLOW-UP ----------

QUESTION: Thanks for you getting back with me I checked everything you said but it still skips under a load runs good while its idle? any suggestions? sounds like a small knock in the 2 cylinder

Answer
Well if you have a nock in #2 cylinder there is a mechanical issue going on like a rod bearing or a wrist pin going bad. That shouldn't effect the spark at all. Are you sure It's a spark issue and not loosing an injector driver to one of the cylinders? you can try a nois light in place of an injector and run the car and see if the driver is dropping out for one of those cylinders.. You can try this as well use a spary bottle of water and spray down the engine and brake torque the engine and see if you see and or hear a spark jumping the presence of watre asct like a conductor and if you have a leaking plug wire or a cracked spark plug it will show up easier It's a poor man's version of a engine scope :)