I have a '03 3500 SO Auto that I bought 02-2003. Last winter the high idle ran perfectly at around 1000 RPM's but this winter it runs rough because the idle fluctuates between 900 and 1100 RPM's. Has anyone had or heard of this? Thanks

 

Just a SWAG, but how many miles on the fuel filter? Are you running good fuel? Running any fuel additives?

Not to beat a dead horse, but fuel quality is a big deal in cold weather.

 

Mine high idled on its own for the first time the other morning 23°....has the same surge as yours.

9300 miles on filter...always buy at the same place, NO additives....

Really does not bother me. As long as it keeps running great warm, starts, and stays running...

JKE

 

I have 11,200 miles, no additives, fuel I buy from a truck/car stop. The truck stop where I'm buying fuel from I believe only has one blend, if it has more than one I don't know how to tell the difference. Do different stores sell different qualities? I have not changed the fuel filter.

 

Are you sure that isn't the intake heater going on and off when it's cold, mine acts that way when really cold out.

 

errr, no. not the grid heaters. 9300 is the milage on my fuel filter...19,600 on the truck. Yes, diff. quality. When I first bought the truck, I got fuel at 2 places. The one that I use now and another. The other got slightly better milage, but I was concerned about getting old fuel or something from there since they were way off of the beaten path and a very small station. FWIW

JKE

 

I don't think it is connected with the heater because it is a constant variation of the idle as it cycles. The lights still dim when the heater cycles on and brighten back up with it cycling off. The idle in the mean time remains a bit rough though-out.

 

Mine does it, too. I've got 7000 miles on mine and it has always surged on the high idle.

 

well, high idled this morning and was smooth as glass. I have changed nothing since my other post! ???

John