Anyone know what my cause an engine to osolate while idling? The only time I notice it is at idle and the interior lights dim at the same pace.

 

Sounds like the grid heaters are cycling , because you mentioned idling & interior lights dimming .
Does it happen warm / cold ?
How much RPM change ?

 

the grid heaters will dim the lights,

and if its REAL cold the truck will idle itself up to protect itself.

i usually run the High Idle on my 06 if it's cold, to keep the voltage flowing and warm the motor.

 

If it happens right after you crank it up it's natural. What is happening is the power drain from the fuel heater and the starter is causing your alternator to rebuild the battery strength to normal. If it does this all the time it may be your alternator or voltage control.

 

Pull the pin up.
When my fan oscillates I pull the pin up to make it stop. Try that.



But yeah, its probably your grid heaters cycling cause of the cold weather. Itll do that for the first few min of a COLD start.

 

It does it even after the truck has warmed up. I can tell when the grid heater cycling. There is not a drop on the tach but you can hear it in the exhaust and it follows the lights dimming. They are in time with each other.

 

ive had that happen to me too but only when its real cold and high idleing, its not the grids cycling, i dont know what it is either. its pretty noticable.I pay it no mind. when cold diesels do some strange things. maybe its engine shrinkage.

 

HAHA

but yeah most likely just the grid heaters like others have said

 

read this guys.

the grid heater will cycle even if your engine is at full temp! It is activated by the intake air temp sensor. If it is cold out it will come on

https://www.dieseltruckresource.com/...ater+operation

 

Do you by chance have it set to defrost? When you have it set to defrost the AC compresor will cycle on and off putting extra load on engine. Mine will make the engine alittle louder but havent noticed lights dim though.

 

It is alot faster than an A/C compressor or the grid heater cycling.

 

I guess that the problaem is more like a lope than anything else. Have started to notice it going down the road now. I am wondering if it is something electrical. It is like there are electrical surges.

 

Did you get this fixed? I know I have a VP but just noticed a similar problem, more frequent cycles than grids, but a little faster than a lope, and only when I let off and it's in neutral, like at a stop sign. I would say its like as if you just barely touch the pedal, every 1 second.