so i bought a 1995 z28 a few months ago. this week i started noticing the oil pressure gauge has been all over the place.

my gauge doesnt have any numbers on it so i have no idea what the psi is. on top of that i dont have the owners manual so i cant look it up there.

ive noticed that in idle the needle is close to the bottom of the gauge, about halfway between the 1/4 mark and the red low oil part. when im driving normally (typically in the 1500-2000 rpm range) my gauge is right at 3/4, sometimes a bit more.

should it be this erratic? its got me really stressed out.

i took it to a mechanic the other day and they told me my oil pressure and level are fine but they noticed my oil pressure sensor was broken. so they replace it but my readings are still all over the place just as they were before.

did this guy pull a fast one? did he replace a part (and charge me) for a part that wasnt broken?

 

The oil pressure sensor is located towards the drivers side at the rear of the the intake manifold. If you have a mirror, you should be able to tell whether it looks new.

http://shbox.com/1/oil_pressure_sensor.jpg

 

There is no excuse for not having a manual.

1993-2002 F-body Owner's Manuals

 

actually my car does the same i never consider it as a problem also the coolant sensor light is on as long as you keep cheking it out you wouldnt have any problems with it

 

Sounds normal and at idle I am just above the red line and it goes up with throttle. Don't worry unless it drops into the red area. I paid big bucks for replacement parts and realized later they were not changed. I even asked for the old ones before the work was done. They then pointed to the dumpster and said I was welcome to go find them. If I ever run into those people on the street...

 

yea, youre not joking. got to dig up a mirror so i can check it out.

for real! thanks for link. car didnt come with one. it did however come with the owners manual on casette. which is totally 90's ridiculous and awesome btw.

on a side note, having a pdf of the owners manual is really, really handy. if you have a smart phone and a dropbox account you can move it to your phone really easy and look it up anywhere, any time.

whew! thats reasssuring. glad to know its not just me.

yea, i should have asked for part. hindsight. sigh... all in all its not too costly a repair, only $200. but then i think damn, he might as well have stolen a ps3 for me. wtf...

so the part that toggles the oil pressure light on and off is separate from whatever gives you the oil pressure on your gauge, right?

 

Normal healthy stock LT1 oil pressure is:

~20psi@800rpms(little lower if Automatic...idle is around 500rpms instead of 800rpms)
~35-40psi@1600rpms
~55psi@5700rpms

Oil pressure is proportional to RPM. If moving at a steady RPM, then the gauge should be steady and not jumping around.

As far as the light, I think there is a point at which, if the pressure gets low enough, the check gauges lamp will come on....but I'm not sure. There is also an oil level indicator lamp, which has it's own sensor in the oil pan.

For the reading to be all over the place....it sounds like gauge problem, oil pressure sending unit issue, or some other type electrical issue. You could grab a mechanical oil pressure gauge and verify the pressure(see if it agrees with the dash gauge). There is a port above the oil filter that can be used to attach a mechanical oil pressure gauge.

 

The check gauges light should come on if the oil pressure drops below 6psi. That's the minimum acceptable pressure according to GM.