I had a similar experience with my 94 K1500. It ended up being low on oil.
The fluxuations could be the oil sloshing in the pan and the pickup tube
intermitently being in/out of the oil. Your post didn't mention if you
checked the oil or not. Let us know if it is low. Also, I had a major leak
in my oil filter housing that sends the oil up front to the oil cooler. I
took that apart and replace the seals/gaskets with a kit. No more leak and
my presure stays pretty steady. At idle, it goes about 20PSI and at highway
speeds about 40PSI. Not sure if this is the norm, but I have no problems
Hope this helps.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.