2008 XLT V6 rough idle at start

[ryker99]

Hi everyone...

I've got a 2008 XLT V6 with about 37K miles on it. For the past month or so, idle has been very rough, hovering around 1K rpm until I put some gas into it.

Goes away after the car has been warmed up a bit. What's the first step to troubleshoot?

It's not the cold weather, as this is the third winter and the first time it's been acting up...

Any help would be very appreciated. Thanks!!

 

[TennesseeVol17]

Answers

I'm new here, but I saw your problem. I'm having the same type of problem with my 2008 EB. It idles rough at 500-1000 RPMs but goes away with applying the accelerator a little. Did you ever find the reason for your problem? Any help would be appreciated.

 

[engineeering]

probably a vac leak.

Note:
The un-metered air causes a big problem during idling vacum. After you throttle up... your vacuum reduces to a pressure closer to ambient which will suck in less air (and the amount of air leaking into the intake is proportionally smaller to your MAF flow at higher rpm)... thus causing the MAF error to reduce at higher rpm.

 

[Megablue999]

I had an intermittent rough idle on startup with my 2005 XLT 4.0L, finally installed new Motorcraft plugs & wires @ 90k that helped, but still not smooth. Picked up an Accel super coil for about $85 new, world of difference, idle was smooth as glass. After about another 7k ended up trading it in on a sweet loaded 2008 XLT Ironman 4.0L. First thing I did week one was new Motorcraft plugs & wires, Accel super coil. Idle is smooth as glass right at 650-700 rpm after about a minute of warm-up time.