2002 Saturn SL1 check engine light came on and code P0303 which is Cylinder 3 misfire detected. I changed the spark plug and spark plug wire and still P0303 comes up. Is there something else I should be checking?
For old models, Saturn/GM also used the same material
fiberglass gasket in your model, you almost certainly have a leak from
a crumpled, sucked-in gasket as I suffered (and many others). I would
say going to Saturn dealership to make repairs is probably not good
idea if they are going to put in the same GM intake gasket part. Maybe
possible to specify Felpro gasket with whatever shop you go to if you
don't do the repair yourself. I would not go too long with your car in
that condition as there is localized leaning at your cyl-3, that could
cause a burnt exhaust valve there.
The exhaust is extra hot venting out
that cylinder. P0303 is misfire at cyl-3. Mine was P0301 (cyl-1). You
may get P0507 once in a while when PCM fails to control the fast idle
caused by the leak under certain conditions. Most of the time, it is
very slow idle caused by 3 cylinders running. You run smoother in cold
idle because the IAC opens up to increase idle and end up lowering the
manifold vacuum, so the reduced vacuum causes less leaking at the
failing intake manifold gasket.
I'd say try cleaning everything with your ignition before replacement; Idle problems could be caused by engine coolant sensor (ECTS). Are you sure it was changed? Did they put on a new wire connector along with it?
Hope helps.
Replace the coil it is most likely bad. observe the engine at night or in a dark environment and proceed to use a spray bottle to lightly coat the coil pack for that cylinder number 3 and if you see an arc at the coil or any where else this will confirm a bad coil but even if you don't see any arcing it still may be a weak coil.
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