rough idle when cold

[ckmarsh]

my wife got a 2006 mercury mariner in july we are going on a trip this sept the mariner started to have a rough idle when the motor is cold but is fine when it warms up its a 3.0l dohc
anyone know why it would have a rough idle when cold?

 

[Rand]

define rough idle?

 

[johnachak]

It hasn't warmed up yet? I use Full Synthetic oil in mine as it runs smoother and warms up quicker when cold (2006 3.0l Ford)

 

[ckmarsh]

define rough idle?

like its running on 5 cyl or a miss

its got some bulk oil in it the dealer put in i am going to use Pennzoil Platinum 5w-20

 

[tinmanSC]

Always look for vacuum leaks first! engine oil won't cause this type of issue unless you put straight 140 gear oil in the thing.

 

[ckmarsh]

I was thinking the cold start enrichment system or
air /fuel feedback control sensors but it has to sit overnight to run rough

 

[Dakota1820]

iac?

 

[zzyzzx]

Throttle body needs to be cleaned.

 

[ltslimjim]

Coolant level okay?

 

[mechtech2]

Originally Posted By: johnachak
It hasn't warmed up yet? I use Full Synthetic oil in mine as it runs smoother and warms up quicker when cold (2006 3.0l Ford)


Too bad your car heats up quicker with the high friction and drag oil you put in it. Consider using an oil that heats up SLOWER. An oil would have to be horrible to make an engine heat up faster.

To the OP:
Vacuum leaks, Dirty MAF, coolant sensor, or dirty TB and idle air valve should be checked.

 

[yonyon]

It's a Ford. Rough idle when cold is usually going to be either a shrunken intake gasket or a worn spark plug.

 

[vssjim]

check for vacume leaks when cold spray carb cleaner around intake and such and see if smooths out or raises RPM.