So my bronco has been sitting for about a year, sadly. Im getting to work on it again. When it was running(broke a shift fork and pulled the trans a year ago) the engine made some lower end noise. Its a 4.9L. the noise was usually loudest when i first started it. You could still hear it when it ran until I started useing 15w40. Anyways i hooked up an oil pressure gauge once and the gauge would jump back and forth until revved up. So im doing the oil pan gasket and rear main seal soon. I bought an oil pump for it, but dont really know what could cause the gauge to jump like that? Ive heard these engines last a long time and are often a little noisey. any info would be great thanks.