Oil Pressure under boost

[Splitpi]

Yesterday I was bored and sitting around and decided to work on my car. I was tired of looking at oil pressure gauge at idle and seeing it just barely hovering above the bottom the gauge. So I replaced the oil pressure sending unit.

Now when I boost or cold start the car, the needle is buried at the top of the gauge. No other work was done (except an oil change (~3.5 Qts AMSOIL 10W-30, ~0.75 Qts Lucas Oil Additive, been running this mix for the last 12K miles) and I replaced my Front O2 Sensor).

Upon removing of the old oil pressure sending unit, it was had sludge caked onto the end though the hole on the sending unit was clear and clean (I don't believe the old lady that owned the car before me took the best of care of the engine, though it had only 58K when I bought it and is now sitting at 71K).

I also cleaned the contacts for the wire hooking up to the sending unit. I realize the gauge measurement is subjective, but anyone have any ideas on why it is so high? Does the ECU interpret the voltage for the gauge and has some sort of stored "offset" that doesn't correlate to this new sending unit? Any ideas on why the oil pressure gauge reads maximum under boost and at cold start?

If I idle after warming up or push in the clutch it falls back down to the lower half of the gauge... so it is reading something.

 

[andymoraitis]

In general the stock gauge is very inaccurate and shouldn't be taken as a correct measure of oil pressure. I would invest in an aftermarket electrical gauge so you can see exactly what oil pressure is numerically.

It's not uncommon for oil pressure to read high when the motor is cold and then slowly decrease as the oil warms and becomes more viscous. As an example I see 75 psi on cold startup and around 20 psi at idle. At WOT I see around 90-95 psi. Keep in mind that removing balance shafts will also increase oil pressure.

Hope that helps,

Andy

 

[sexytoy69]

In general the stock gauge is very inaccurate and shouldn't be taken as a correct measure of oil pressure. I would invest in an aftermarket electrical gauge so you can see exactly what oil pressure is numerically.

It's not uncommon for oil pressure to read high when the motor is cold and then slowly decrease as the oil warms and becomes more viscous. As an example I see 75 psi on cold startup and around 20 psi at idle. At WOT I see around 90-95 psi. Keep in mind that removing balance shafts will also increase oil pressure.

Hope that helps,

Andy

I just installed an electrical oil pressure gauge and it is at 10 PSI during idle. Is that normal or too low?

 

[GST98BIG16G]

10psi , is kinda low . Mine idles at 20-25psi. Cold is like 70-80psi. Check your oil level

 

[eboy0]

I had a little sludge cake aswell in my oil sender unit, when i got tired of not seeing any oil pressure... so after putting in ann autometer one..
I've got about 25psi @ idle.
Needle buries itself at 100psi at boost.

 

[sexytoy69]

10psi , is kinda low . Mine idles at 20-25psi. Cold is like 70-80psi. Check your oil level

My oil level is fine. Should I be worried if it's that low at idle?

 

[Merkles]

At idle my oil pressure is at the line in between 0 and 25. I have to assume its about 12.5 psi. Thats what I idle at when my car is warmed up. I idle at about 75psi on a cold start and it works its way down.

 

[GST98BIG16G]

check oil sender unit

 

[rennat]

Doesnt anybody make a oil guage that goes higher than 100PSI??? Everybody seems to peg them out, so im just guessing if we had a higher guage, then, we could maybe even get more input on just how high the oil pressure does go... just a thought.

 

[DGajre777]

Doesnt anybody make a oil guage that goes higher than 100PSI??? Everybody seems to peg them out, so im just guessing if we had a higher guage, then, we could maybe even get more input on just how high the oil pressure does go... just a thought.

Prosport makes one that goes up to 110psi. Defi Blue racer makes one that goes up to 140psi.

 

[antlip]

I read in a rebuild book for 4g63 motors that 11psi is the minimum oil pressure in gear at a stop.

My car is about maxed out when cold. Its been in the teens here. Warm idel and in park, my gauge reads about 25 give or take a couple pounds. In gear at a stop im at 15 or 16 fully warmed up.

 

[eboy0]

I read in a rebuild book for 4g63 motors that 11psi is the minimum oil pressure in gear at a stop.

My car is about maxed out when cold. Its been in the teens here. Warm idel and in park, my gauge reads about 25 give or take a couple pounds. In gear at a stop im at 15 or 16 fully warmed up.

My autometer doesn't seem to drop below 25 no matter what the condition.. is that a bad thing?

 

[wvturbo2]

Mess around with the wire make sure its not touching something it shouldn't then you oil pressure will go back down where it should be. Mine was acting weird and would peg the far right as long as the car was in the on postion. Wiggled it and it went back to normal