Reader Question: I have a 1996 Lincoln Continental 4.0 v8, that the engine light came on and it started to run like it had a miss.
I was told by an auto parts store that plugged a meter in that the number 1 cylinder was on the code, but the meter did not say just what the problem was.
Therefore, I changed plugs, wires, check the fire from the coils, and checked the fire from the fuel injectors. Fuel filter was changed the oxygen censor changed and mass-air cleaned.
The car passed emissions test just fine, but it still has a miss in it, and the light is still on. Also, the gas mileage dropped from 21 to 13.
I am not sure how it passed an emission test with a misfire, a check engine light on and a severe drop in fuel mileage…you got very lucky I guess. You have replaced all the easy stuff, so I would look and listen for a vacuum leak somewhere under the hood like a broken vacuum hose connection.
If you do not see anything or HEAR anything hissing under the hood, I would then want to do a compression test on the engine to make sure this is not an internal engine problem with the valve train or piston.