I noticed today when the car was warm and cruising along abot 50 ish mph it felt a little lumpy so glanced at gauges to see the oil pressre was reading of the scale when usually it sits around half way, is this a big problem and what can cause this, many thanks

 

Welcome aboard thirdgen.org.

Most likely your oil pressure sender has died. First thing to do is to check the gauge with the ignition on and engine off - what does the gauge now read? Next, unplug the wire from the sender and see if the gauge goes back down to zero. If the gauge is up with the engine not running, or if it goes down to zero when unplugged, your sender has most likely failed.

To verify, you can do one of two things: 1) Buy a mechanical gauge, install it, and see if the oil pressure is normal; 2) buy a new oil pressure sender, install it, and see if the oil pressure gauge now reads normal.

There is a small chance that the gauge is reading the actual pressure, which would mean the oil pump bypass has stuck. You have to drop the oil pan to fix that.

 

thanks, were do i find this wire, i am very new to american cars, my car is a 1991 trans am 5.0 v8 tpi if that helps

many thanks

 

Okay, now I've done it. My 3rd gens were '86-earlier, and things changed in the later years.

If I'm recalling correctly what I've heard around here, it's above the oil filter.

If I'm wrong, hopefully someone will correct me quickly.

 

When the engine is off but ignition is on the gauge moves to around the 1/4 Mark and then once started goes straight to 3/4, once I accelerate it goes to full or even over, it does seem to bounce around at the top end of the gauge

 

Sounds like what my 91 GTA started doing when the oil pressure sending unit went. I drove around with it like that for 2 months because I didn't know any better at the time. (19 and didn't know squat about cars) I did the oil pressure sending unit and now oil pressure reads at around 45-50psi cold and idles at 28psi warm. The oil pressure is located right above the oil filter and is a major pain in the a** to get out. You'll need a crow's foot wrench or an offset wrench to get in there.