altima idles rough

[bigwil32]

just recently put a new after market CAT along with new O2 sensors and plugs on my 2.5L altima because the original CAT and sensors were toast. Also about 3 months ago a replaced the camshaft sensor because the car would not start. After doing some research I should have replaced the crankshaft sensor as well. My question is could the be the reason the car idles rough and causes my CAT to get hot? Oh yeah I had a multi cylinder misfire, that is why I replaced the plugs which lead to the CAT

[Darius]

I'm not sure exactly which sensor tells the injectors and plugs to fire, but from your description it seems like the crank position sensor is the root of the problem. It appears that it is not sending the correct signal to the ECU or it is on the retarded side. When it is retarded, the gas doesn't completely burn in the cylinder and it gets passed into the exhaust (while still burning) causing the exhaust to get very hot (and glow red). This is bad and very hard on the manifold, cat, and O2 sensors.

This is why I'm thinking it is either a bad crank position sensor or it is rotated somehow. I have never touched a CKP sensor on these motors so I can't tell how it is adjusted if at all.

Also, not to insult your intelligence or anything because I don't know your experience level but make sure you properly gap the plugs before installing them. Too wide a gap and it could misfire and foul the plug.