oil pressure wandering @ idle

[chessy56]

I've got a 2001 LB7 with 278K miles. I'm starting to see the oil pressure gauge in the IPC "wandering" a bit at idle. At driving speeds, the gauge appears to be steady throughout the rpm range. When I'm idling (park, stopped in traffic, etc), the gauge is not always steady and drifts +/- 1 mark (max). I've been running Rotella 5W-40 T6 for years without problem and changed it (and filter) about 1,000 ago. Any possibility that the oil pump is showing it's age and possibly on its way out? (If so, how much of a PITA is it to change out?) Could it be the IPC itself?

[DmaxMaverick]

It could be the pump, but I really doubt it.

It's much more likely the sender or the IPC.

I haven't seen or heard of a pump failure, but plenty of IPC's, and one sender.

[chessy56]

Thanks for the quick reply 'Maverick. I think I'll look at the sender first, as my guess it'll be the least costly attempt.

[chessy56]

After receiving 'Maverick's reply, I found the following:

http://forums.trailvoy.com/showthread.php?t=48886

http://www.gm-trucks.com/forums/index.php?showtopic=95547

Seems there's a way to replace the stepper motors that drive these gauges. PITA? Perhaps, but it's an option.....
Feel free to comment on the feasibility.....

[JohnC]

Check for "extra" oil, or fuel in the oil.

The stepper motor issue usually manifests itself differently; the gauge doesn't return to zero when shut off.

[More Power]

A couple of things.... 1- During the summer months and hotter temps, the engine/oil will be warmer than it is during other months. A thinner oil allows oil pressure to respond faster due to changes in engine speed. 2- We've heard from quite a few owners through the years who reported some degree of idle surge, due largely to a less than perfect Fuel Pressure Regulator (FPR). GM says that less than a 100-rpm variation at idle is within a normal range of idle speed variation. A <100-rpm idle speed variation will produce a varying oil pressure at idle in response to changes to rpm. I've seen this in my truck, and I use the same oil as you.