Hi. I have a 1998 Z-28 5.7lt/auto trans with 126k miles. It's like a 4th child to me and my wife gets jealous and irritated with me sometimes about it! For the past several months however, I've had an oil pressure problem that limits the distance I can drive. When the car is first started I have normal oil pressure (showing 12 o'clock on the gauge) but as the engine warms up and I drive it, the pressure falls to about 15 to 20 psi and stays there. It does increase with acceleration but only a little. Once, while on the interstate at high speed the pressure fell into the red and I had to pull over. Checking the oil ALWAYS shows full on the dipstick and allowing the engine to cool before restarting it ALWAYS brings my pressure back to normal!??? I was told I could need a new oil pump, have a clogged pick up tube and oil screen or could have worn bearings and need a rebuild. Any opinions? Also, as of yesterday, I have a solid Service Engine Soon light on. I took it by Autozone and the guy tried 3 times but couldn't find any codes!!???? Any ideas? Thanks! cmgillespi@aol.com

 

yes you could have a clogged pick up tube,which is not letting enough oil flow through.oil pumps do not normally go bad.oil pumps do not create pressure.you could have some work bearings.try hooking up a manual oil pressure gauge and see what you get.these electronic sending units do go bad,so you may not have an accurate reading.

 

I would replace the oil sending unit first. I've had it where I could watch my oil pressure drop down near zero as I was driving on the highway. Replacing the unit took care of it. Not to say that's it, but with that many miles, it's possible yours is going bad.
With a SES light on, I would think they should have read something. Were they unable to establish a connection, or scanner just didn't show a code?

 

yeah thats pretty weird i missed that part,doesnt make sense for the SES light to be lit up but not have a code stored

 

Thanks Saint_Ali and Camaro for the replies.
I will say that I'm sure I DO have an oil pressure prob and prob not a bad sending unit because if I drive it aggresively, like high speeds on the interstate, the pressure not only drops down in the red but the engine starts banging like an 80's hair band drum solo! I would have thought it was a faulty sending unit myself were it not for the engine about to fly apart when it drops that low. If I take it easy and drive short distances it drops to about 15-20 psi and won't drop lower unless I get down on it so I try to drive like Grandma. As for the Autozone counter salesman not being able to pull a code, my Father-in-law, a mechanic and former Autozone mgr., suggested that either the guy did not know what he was doing or he was using an el cheapo OBD reader that could not pull my stored codes. There has to be one in there!? It's physically impossible to have a SES light w/o some kind of code to trigger it right? Can't afford a dealer visit right now. May just have to baby it till this fall then mothball it and go buy a 5th gen... Definitely not selling it or trading it. I love my Z almost like one of my kids.

 

2009 GM vehicles do this. its normal, if it goes to red line its a problem. like u said u took the vehicle on the express way and probably dawged it. A regular $24.99 dollar oil changes can't take that heat. next oil change put some slick 50 replace it with 1 quart of oil. at idle pressure should be 15-20 psi. send me messege ill send u a SS of GM'S specs.