4.6 running rough at idle in gear

[feef706]

I was reading my maintence manual today and at 76,000 miles I decided to take a look at the spark plugs and air filter. I pulled three plugs and one from the back all at seperate times just to see how they looked. I also pulled the air filter. I started the car afterwards and it seemed fine. Then I had to go somewhere and when I started driving down the road the check engine light came on and it started ideling rough at a stop sign. I turned around, realized i forgot to put the sensor plug back in the air filter. plugged it back in and the emissions check went away and the check engine light is now off. the car still isnt running right though. it sounds kinda strange and you can feel the engine in the car it kinda feels likes its misfiring. all the plugs are in the right order. when i push the gas it runs fine but as soon as its back to idle its rough again. anyone have any ideas what it could be. Thanks James

[the little STS]

hmmm come to think of it
my car when i drive it hard it start makin a loud vibration noise
i dont know if that is the same sound as u but it happens at idle as well
id like to know wat is goin on

[feef706]

It doesnt really make a loud vibration noise the only noise i can really hear is it kinda sounds like it isnt breathing right? like the engine just sounds like its fluctuating. its hard to explain. but any help would be appreciated. I forgot to mention its a 96 sedan deville. Thanks alot, James

[the little STS]

oh
but im just sayin this cuz it say 4.6 rough idle soo
ya

[feef706]

I just ran the codes and the only ones that came up were

PC0603
IP1552
PCM?

[feef706]

Disregard... The sixth cylinder plug was cracked and caused it to misfire. New plug and problem solved... Thanks James

[BeelzeBob]

Originally Posted by feef706

I was reading my maintence manual today and at 76,000 miles I decided to take a look at the spark plugs and air filter. I pulled three plugs and one from the back all at seperate times just to see how they looked. I also pulled the air filter. I started the car afterwards and it seemed fine. Then I had to go somewhere and when I started driving down the road the check engine light came on and it started ideling rough at a stop sign. I turned around, realized i forgot to put the sensor plug back in the air filter. plugged it back in and the emissions check went away and the check engine light is now off. the car still isnt running right though. it sounds kinda strange and you can feel the engine in the car it kinda feels likes its misfiring. all the plugs are in the right order. when i push the gas it runs fine but as soon as its back to idle its rough again. anyone have any ideas what it could be. Thanks James

Well...the first rule when you work on the engine and it acts funny afterward is to double check everything that you did...pull the plugs that you had out and make sure that the gap didn't get damaged reinstalling them, that they didn't get cracked or something R&R'ing them, that the terminals for the spark plug leads are in place in the wire boots and crimped securely, etc... Many times just pulling the wires off will damage them due to the wire pulling out of the crimped terminal, the terminal actually staying on the spark plug and pulling off the wire end, etc.....