What is wrong 2001 2.4 cavalier rough idle i replaced idle air control valve map sensor and O2 sensor need help checked coil and plugs look good.What is wrong?

Answer 1

If there are no trouble codes (check engine light)...Check to make sure that raw fuel is not getting dumped into the intake through the fuel pressure regulator vacuum line(leaking regulator).That MAY throw a rich fuel code. Then check that those 4 or 5 vacuum lines on the throttle body are not leaking by removing them one at a time and putting your finger over the port that it came from to see if it smothes out. Then check the fuel pressure(it HAS to be within spec) If those things are right, then I would suspect a problem with a fuel injector. Pull the fuel rail and have a buddy turn it over a few strokes and see the spray pattern comming out of the injectors(but disconnect the plugin at the coil so it wont fire) The plastic housing that contain the coils, has metal strips that leed to the spark plug boots,have been known to burn,but that would throw a misfire code,also if a spark plug boot looks bad or hard,cracked, spark could be grounding out. The plug boot spring may not be contacting the plug also. But you may have to do a compression check or better yet a leak down test. Check the wires going to the plugins at those items you replaced to be sure that none of the wires have broken inside the wire insulation. But I'm leaning towards the low fuel pressure or injector problem. But you must rule everything out until you find the problem. A repair manual may give you some sugestions also.