Rough idle when cold

[Johnny]

I have an 08 5.7 hemi 4x4 and lately it's been acting funny when I start it in the morning and its been cold out. It'll start idling high and sort of surges higher and lower. All of the lights in the truck get dimmer and brighter too as it does this. If I wait long enough and let it get warm it'll be just fine again but that can take 30 min when it's this cold out. Sometimes even after it seems to be back down to a regular idle if I try to drive then rpm's will jump and make the truck lurch forward. Any advice on what to do about this?

 

[bigbadram1500]

Welcome to the forum. Not sure that I know an answer to that, but other should chime in soon to help you out.

 

[BAILEY1]

Welcome.

Try putting a can of seafoam in the gas tank. Sounds like you got a little ethanol build-up. One of my coworkers had "about" the same issue.

 

[03MopaRamman]

I had similar type stumbling issues on the 87 Tune Superchips. My cure was to start running 89 Octane and it solved the cold stumble. Running through some fuel injector cleaner is always a good idea as well every Oil change once these trucks start to age.

Edit: Ha, Ha, Yes the 2 consecutive cans of seafoam cleaned my injectors for a bit too.

 

[Motomech]

My truck surges up and down in the cold morning as well I would say a 300 RPM range till it warms up.