Well, the dreaded idle surge returned once again. This time, when it surges, it's running very rich to the point I can see black smoke from the exhaust. The MAP sensor is only getting 12 inches of vacuum at idle when it should get 18. (according to a mechanic who I'm told is knowledgeable on Fords) If they manually give the MAP 18 inches of vacuum at idle, the idle is perfect. The mechanic cannot find any vacuum leaks and thinks the problem may be the intake gaskets. So, I told him to replace the upper and lower intake gaskets and replace all the vacuum lines. I'm hoping this will fix it. Does this sound like it could be the culprit?

Thanks,

 

I got the truck back yesterday and it's running better than ever! The new intake gaskets seemed to have done the trick...the old ones were in pretty bad shape. The mechanic didn't replace the vacuum lines so I'll tackle that myself. But the idle is perfect! 750 rpms in drive and smooth as can be!