I have an 2002 Avalanche 1500 with about 120,000 miles. Of course, it has a 5.3L gas engine. At idle only, the oil pressure needle jitters (fluctuates). At idle the oil pressure is about 40 (I assume psi) and the needle jitters about 10 psi higher or lower and does it very quickly up and down (like 3-4 times each second). If I increase the engine speed by 200 rpm or so, the jittering immediately stops. The needle seems to jitter at idle all the time when the engine is warm and does not jitter at all at idle when I first start the cold engine. The jittering does not occur at any other engine speed except idle.

Any thoughts?