Rough idle on '03 V6 until warm

[Ntwrkguy1]

I was taking my kids to school this morning in my new-to-me '03 LS V6. It wasn't particularly cold (maybe 48), but when I started the Lincoln, it idled really rough (but didn't die).

After about 7-8 minutes of driving, the idle smoothed out. I made a few stops along the way after dropping the kids off, and since the car was now at operating temperature, there was no more rough ilde.

I'm assuming since the roughness went away that I don't have a vacuum leak. A lot of the hoses under the hood were replaced by the previous owner recently, but two things I have no record for is the PCV valve and IAC valve. This is really only the second time I've driven it since bringing it back from FL, but I don't recall whether the rough idle was there last time.

I did some searching, and found quite a few "rough idle" posts regarding the V8s, but nothing about rough idle on a V6 that goes away after reaching operating temperature.

Is it possible this is either the PCV or IAC? Or is it possible that the MAF sensor just needs a good cleaning?

 

[joegr]

I would expect a vacuum leak because of your symptoms. In addition to the hoses and the PCV, check the intake gaskets and the o-rings at the back.

 

[Ntwrkguy1]

I would expect a vacuum leak because of your symptoms. In addition to the hoses and the PCV, check the intake gaskets and the o-rings at the back.

I thought if you had a vacuum leak, it would continue to give a rough idle, even after the car reached operating temp?

I will definitely check the vacuum hoses, and figured it's a cheap fix to replace the PCV. I know what the intake gaskets are, but what are "the o-rings at the back"?

 

[joegr]

Sometimes, a small leak will seal off and things heat up and expand. Also, an engine at operating temperature is not as sensitive to small leaks as a cold one is.
Of course, it could be something else too.

The o-rings are at the back of the manifold on some runner valves.

 

[Ntwrkguy1]

Got it.

I'm going to take a good look at things this weekend, and replace any worn vacuum lines. Does it make a difference if I use OEM for the PCV and IAC valves, should I choose to replace them?