iponnet22

Hi, I have a 02 z28 and recently have had a problem with my oil pressure bouncing at idle after a drive or when the engine is warm! It bounces between 30ish to 40 rapidly and it annoys the hell out of me..lol. it is about 60 while driving it cold and as expected it decreases as the engine gets warm and than starts bouncing at idle..

I have cleaned the engine with motor flush and also have tried multiple oil changes to try and see if it helps. Am I correct to assume the most likely suspect at this point is the oil pump and not the oil pressure sensor, since it seems to read the pressure correctly and I only get the bouncing at idle?

should I just replace the oil pressure sensor anyways since its an easier/cheaper job?

any help appreciated,

transamtom

Mine acted wierd sometimes as well

I replaced the OPSU when I did my LS6 intake swap and all is well.

Marc 85Z28

Oil pressure cannot fluctuate like you say the gauge is indicating, even with a failed pump or a cavitation issue. You have an electrical issue, most like the sending unit or the gauge itself.

iponnet22

Thanks guys for the replies, I just bought a OPSU and the socket for it. Going to get it done in the next day or two. Will update the thread.

whitdog54

thats normal. Should be a little below half at idle, and a little above half when driving and romping on it. These gauges move allot, and your coolant temp gauge is dummy gauge its readings arent accurate at all. thank gm

you could have a problem, but im just guessing you have the normal fluctuating gauge.

Marc 85Z28

No, it's not.

whitdog54

^hmm my v6 and v8 did the same thing. It doesnt move erratically, the pressure just changes from idle and acceleration. Its done the same thing everyday since I owned it. No problems, maybe ill change the sending unit out sometime to see if it helps. But im not worried, no knock, and like I said my v6 did the EXACT same thing, and i put over 40k HARD miles on that.

Howd the oil look last time you changed it, any metal shavings?

EDIT: just re-read the OP, saw rapid changing, sounds like a bad connection or sending unit (hopefully). What I was referring to is when you accelerate the pumps spinning more, causing a higher pressure.

iponnet22

alright gentlemen, I finally got around doing it yesterday..space was really tight and got scratched up pretty good but the worst part is even after a new OPSU I still get the fluctuations at idle after the engine has been warmed up or after a long drive. I also took out the cluster panel to see if I could hook up a multimeter to the oil gauge and see if the readings jump up and down but I didnt know the whole thing just plugs into the back and I couldnt figure it out. I ended up just cleaning the plug and blow off any dust to see if that helps, it didnt.

But anyways what do you guys think I should do next? just suck it up and do an oil pump or is there more diagnosing I can do?

thanks again

rod442

My mustang is doing the same thing. I had to do 2 oil pumps with the engine+pan in the car. so getting the pickup to pump sealed; or pump to block sealed correctly, probably didn't happen. 20k miles on this motor since, and Im not worried.

You could do an oil pump to make sure the o-ring is good and not pinched, but its a lot of work. Maybe wait and do it all as part of a timing chain and cam change, or something.

Marc 85Z28

Replace the gauge.

rod442

would it be a good idea (before you replace the guage), to find somewhere you can tap in and hook up a mechanical one? I recall there is a place near the oil filter.

Google search for instructions. of course, that wouldn't show if there is a pressure differential between just out of the pump, and up near the top end where the stock guage is getting its read.

rod442

here is a good link to a recommendation on how to do.

1/8" Oil Pressure Sender on LS Series - LS2 Forums

Marc 85Z28

Checking the oil pressure with a mechanical gauge is a lot of work, and completely unnecessary in this case.

If the needle bounces at the rate of this head shake: you may have a pressure problem.

If the needle bounces faster than this laugh: you have an electrical problem.

rod442

Marc, not trying to start an arguement; but why would an electrical or guage issue change how it behaves with a warm engine and thinner oil?

and if he is truely trying to figure out if replacing the pump is necessary, getting a mechanical reading is much less work than that.

Marc 85Z28

Because when cold the oil pressure doesn't read around 30-40psi, it reads higher. The stepper motor (what drives the gauge) could have a fault within that range and within that range only. The only important information he gives here is that the reading fluctuates rapidly, everything else just confuses the issue if you don't understand how the system works.

The coolant temperature gauge in my 2000 Olds Alero used to do the same thing, only at 210 degrees - it uses a nearly identical stepper motor produced by the same manufacturer.