Truck surges on startup from cold, fine after running a few minutes

Sorry all, this is a belated post. I continue to have the same problem but haven't been able to spend the time to test where it could be.

As a refresher, when the truck is COLD, truck will surge (more like rev and then let off) and the voltage is jumping up to 15.8V and then once it warms up, all that disappears (literally a minute, maybe 90 seconds at a most). It's not doing it ALL the time when cold, it's doing it like the glow plugs are enabled, then disabled, then enabled again (I think someone called it cycling).

Anyways, once that ends, this never occurs again until the truck is left and is cold again. Never an issue charging with the battery, starts fine, runs fine, just this annoying warmup.

I still think it's a issue with either a sensor or a wire to the alternator that doesn't supply the correct voltage when it's warming. I'd rather have the alternator just charge to the battery and not have to worry about jumping voltage issues when the surging is going on...

Still investigating...

 

Surging is what we call this. You are running 15 W40 oil I woud bet. Switch to 5 W40 oil and the surging will stop. You can run 5 W40 oil all year long without a problem. Happy Thanksgiving!

 

10w30, per the prior remarks. It’s not an oil issue.

 

I believe that there is a glow plug protection strategy that turns them off above a certain voltage. I haven't seen it documented, but I have seen it posted in one of the several 6.0L forums.