The oil pressure gauge in my 99 3.8 liter fluctuates. It only does this when warmed up at idle. It is a constant 65-70 when cold and a constant 60 going down the highway warm. Part of me wants to say it is just instrumentation and not to worry about it after all if the car had an idiot light it would not have come on. I think I am going to buy a mechanical gauge just to test if it is the gauge but in the mean time I have to ask.... If this is not an instrumentation issue and something is going wrong what could it be? The video below was shot sitting in my driveway at idle after about a thirty minute drive. notice the tach is constant.


YouTube - 1999 Camaro V6 3.8 Liter Oil pressure Gauge Fluctuation

 

Its a gage/wiring issue, the only time I see that type of fluctuation on a manual gage the motor is in the process of ripping itself apart and it is never quiet. Normal they are banging and clanging so bad you are a little nervous standing next to them.

Your on the right track. Verify your pressure with a mechancal gage. Then decide if you can live with it or not. It might be a pain to track do the exact connection that is causing it. Might be a loose connection on the sending unit. I chased one down in a vet one time that ended up being the connection at the firewall. Took me two days to find it and that was after installing 2 new gages and a sending unit all per GM tech support.

 

Mine does this same thing too... It always has with 3 different engines. I do not wiggle as much as you do but I still have the same type of wiggle. I always attributed it to the way the sending units are designed. (cheap).

Massey

 

Looks like a funky wiring connection to me. Slide the connector on the oil pressure switch off and on a few times to make sure you give it a good clean connection.

 

I removed mine and put a mechanical gauge in along with temp. I never trust those dam things and they also leak. And when they let go, ur SOL. CUZ unless u have a pipe threaded bolt, ur not going n e where.

 

Oh yeah mine does that, albeight from like 60 to 55, just sudden snappy jerks back and forth, but so much as tap the gas to 1000 and its still at 60 anything more and i run a consistent 68

 

Mine does the same to just not as bad, most likley its the oil pressure switch. I heard they are an issue on our cars and ive replace mine twice so far. Both times oil has leaked past a thin plastic cover on the inside of the pressure switch that engages the electronics inside and into the area that has the sensor and electronics itself which caused the gauge to dance around alittle. I found this out cause the first one i replaced, the oil pushed through the sensor itself and was in the area where the engine harness plug goes in. the second time i seen this was when i again replaced the switch and accidently snap the housing and seen oil residue on the electronics and seen where it was leaking past the thin plastic cover. As long as its reading the correct pressure i wouldnt worry about it. Its just a faulty design that they use for the switch.

 

Well after reading the replies I would say it appears this is at least somewhat common so I am not going to worry about it too much. I did get to thinking and remembered that in the process of installing the engine in the car I did somehow managed to break the sending unit that was on the car so I had to buy a new one. This one is only 3 months old and I just checked the Autozone website and it says the part has a lifetime warranty. I think I will just take it out tomorrow morning and just go exchange it. I am pretty sure it did not do this when I first put the motor in because I would have been concerned right off the bat

 

One last follow up. I exchanged the sending unit this morning. I now think Massey is dead on with his assessment that they are just cheaply made. With the new sending unit the fluctuation is about 80-90% gone. It still does a bit but nothing like it was. Also the reading with this unit are about 20-25 pounds higher under all situations. So much for quality control at the sensor manufacture.

 

It could also be the wiring connection that plugs into the sending unit. I cut one off at a salvage yard and soldered it in place of the old one. Mine was jumping around then it was either showing oil pressure or no oil pressure. After splicing in the new molded connection, it reads without any fluctuations.