Rough idle after driving on highway

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Jun 6, 2016
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I did a quick search for a rough idle but I didn't see anyone that was having the same issue as I am. When I start my car and drive around town, it idles perfect and runs great. Most of the time when I've been on the highway for a while and I exit the highway coming to an eventual stop, my idle is extremely rough and the truck feels like it wants to die. The RPMs jump from like 300 to 900 or so. Any reason this might be happening? The speed doesn't seem to be a real issue as it will do this if I've been driving at 70 or 80 and the same goes for the PWR button being on or off. No difference
 
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Dec 8, 2006
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New Jersey
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I did a quick search for a rough idle but I didn't see anyone that was having the same issue as I am. When I start my car and drive around town, it idles perfect and runs great. Most of the time when I've been on the highway for a while and I exit the highway coming to an eventual stop, my idle is extremely rough and the truck feels like it wants to die. The RPMs jump from like 300 to 900 or so. Any reason this might be happening? The speed doesn't seem to be a real issue as it will do this if I've been driving at 70 or 80 and the same goes for the PWR button being on or off. No difference
Try to get it to happen again. While it's idling rough, try slightly loosening the fuel filler cap and see if there is a release of excess pressure. If the rough idle clears, then it's possible you have a blocked or damaged fuel return line or your charcoal canister is clogged.
 

landtank

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your EGR valve is sticking. While driving on the highway the valve is open and gets hot and sticks open slightly when you come to a stop which is usually at the bottom of the ramp. Next time it happens try giving it a few quick high revs in a row. That will usually help seat the valve and cure your idling problems.
 
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Feb 7, 2009
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I'd say egr also, next time it idles rough pull the line and blow they see if it unsticks had the same issue on 62 series and blowing would clear it up so egr was sticking and just replaced it no more problem
 

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