Your oil pressure goes up with more throttle (higher rpm) and there is less pressure say at idle. Therefore your gauge reading will vary according to the throttle/rpm.
A short in the turn signal wiring can cause the voltage gauge to fluctuate. A loose ground wire can also cause the gauge to fluctuate.
Possibly the thermostat is opening and closing with the water pressure changes. Could be low on coolant also.
Attach a fuel pressure gauge at the throttle body on the top of the motor to determine fuel pressure. Gauge can be borrowed at auto zone and they can assist as well.
The oil pressure gauge is going to fluctuate on a Toyota Tacoma or any automobile. The oil pressure is less when the auto is idling and more when the auto is going down the road.
An automobile temperature gauge can fluctuate when the thermostat is opening and closing erratically. The temperature gauge can also fluctuate when the ground wire is loose.
The ETC system in the GMC Envoy is the Electronic Throttle Control. The ETC acts as a throttle pressure gauge when the gas pedal is pushed. It takes the place of the throttle cable. This part is located right next to the carburetor.
It goes up while driving and down when you're idle....that's normal
Temperature.
A pressure gauge indicates actual pressure and a differential pressure gauge indicates the difference in pressure.
Low oil. Just driving steady, it will drop as you drive, because the oil will change thickness as it warms up, reducing pressure
what would cause a oil pressure gauge to fluctuate on my 99 Chevy truck silverado i change the sending unit it does it mostly after it warmed up
Because Pressure gauge measures the the differenceof pressure so it is called pressure gauge not meter.