LLY Surging When Cold

[WILLYD-MAX]

On my 05 when its cold it will surge slightly at around 1300 to 1500 rpms at say 30mph. I had a reflash done a winter ago and it seemed to help but it seems to be back. Its not nearly as bad as it was before I had it flashed . I use a high quality fuel additive in every tank also. Any suggestions?

[Tough Guy]

What brand and weight motor oil are you using?

Chris

[WILLYD-MAX]

I am using Amsoil Synthetic 15W40.

[Tough Guy]

Try Mobil Delvac 5w-40 next change. It has cured the morning "romps" for some Ford owners.

Chris

[DmaxMaverick]

Try Mobil Delvac 5w-40 next change. It has cured the morning "romps" for some Ford owners.

Chris

Good advice if you have a PS with HEUI. The oil won't effect the idle/running on a Duramax. The problem has to be either fuel system or electronic related. I don't have an answer, but oil isn't it. Air digestion is a more likely candidate.

[More Power]

Some fuel pressure regulators (FPR) seem to be the root cause of surging, which is most noticeable at idle or slow driving speeds. 100-rpm idle variation is the threshold for a warranty repair.

My '01 started doing this about a year ago. Still does it a bit, but only when cold, and the idle variation has reduced considerably over what it once was (about 100-rpm). I attribute the improvement to the use of a fuel additive over the past six months. Or maybe it just got better on its own.... :rolleyes:

If your surging is due to variations in rail pressure, you should be able to see it using a Tech II. A new FPR might be the cure.

Jim

[WILLYD-MAX]

Thanks for the advice. I will have it looked at if it gets worse.