Oil pressure issue

[97copcar]

I have a 97 z28 with a LT1.
Oil pressure is normal while driving but, when the engine warms up and is at idle it drops so low the car sometimes stumbles and the check gage light has come on a few times.

I have pulled the code and I have egr code, I have a new valve and solenoid and will put them on the first chance I get.

Were do I start troubleshooting the oil pressure issue?

[97copcar]

Thank you Captain Obvious.

If you have something helpful to post, I am all ears otherwise don't waste my time with your nonsense. Also, try using a spell checker.....

I am on here to hear from someone that can help me increase my knowledge and point me in the right direction to start finding the issue.

[Tech II]

Do you have an oil pressure gage or an idiot light?

If gage, what is pressure on startup? Does pressure drop linearly as temp rises? In other words, does it start out around 40-60psi, and then as the oil warms and thins out, does it gradually drop to zero or near zero?

Or does it drop abruptly without warning?

Or is pressure dropping because the engine is stumbling?

Have you verified oil pressure with an external pressure gage?

Also, have you been consistantly been using the same oil and filter?

How is oil condition? Does it smell like fuel?

Has the engine had any recent work done to it?

[97copcar]

See answers in Red.

Originally Posted by Tech II

Do you have an oil pressure gage or an idiot light? The gage in the dash cluster is reading near 40 at startup, then as the engine warms up it starts to drop. I have an idot light on, it is throwing a EGR code.
If gage, what is pressure on startup? Near 40 Does pressure drop linearly as temp rises? Yes In other words, does it start out around 40-60psi, and then as the oil warms and thins out, does it gradually drop to zero or near zero? It only makes it to near zero while at idle, i.e. at a read light.

Or does it drop abruptly without warning? no, drops gradualy.

Or is pressure dropping because the engine is stumbling? I am not sure, the pressure drops and when it approches the red line is when the engine starts to stumble.

Have you verified oil pressure with an external pressure gage? No, I don't have access to one.

Also, have you been consistantly been using the same oil and filter? Yes

How is oil condition? Does it smell like fuel? I have not checked it, I will check tonight when i get home.

Has the engine had any recent work done to it? Yes, new starter was put in and an oil leak at the valve cover was repaired. This issue was present before the work was done.

[Genopsyde]

I think your oil pressure is only dipping down that low because of the stumbling caused by the faulty egr. Take care of that first and see if it continues. If so, it could just be a bad sender/switch.

[97copcar]

Thanks Genopsyde, i'll get those parts installed as soon as i can and report back.

[97copcar]

Sorry it took so long, life has been fast and furious for me.

I replaced the egr valve on Monday and drove it Tuesday but, it still had the light on. When I got home yesterday, I cleared the code. The drive in this morning did not show any improvment. It still idles rough and the oil pressure drops after warming up. Do I need to give it a few days forthe pcm to realize the egr was replaced and adjust to it or do I need to start looking at something else?

[Genopsyde]

Exactly how low does the oil pressure drop? Does it only do this at idle? How does it act under acceleration? Any possibility of recording a video?

[97copcar]

If left alone, the oil pressure will drop to the orange slash mark on the left of the gage, it has even turned on the check gage light on before.

It stumbles during acceleration in the 1,500 to 2,00 rpm band, outside of that acceleration is fine.

I can see if i can get a video, it may take a few days as I have to line up a passenger to do the taping.

[Genopsyde]

I think a compression check is in order.

[97copcar]

Thanks, that testing is beyond my abilities. I'll make an appointment with my mechanic.

[Genopsyde]

well let's do all the troubleshooting that can be done without costing you money. I know space is tight, but let's see if you can do this.

while the car is running at idle, unplug the injector connectors one at a time and listen for a change in idle. If the idle does not change for the worse on any cylinder, then you have a misfire on that particular cylinder.

I only suggest the compression test to rule out internal engine failures.

[Genopsyde]

I'm thinking you may have an optispark issue fwiw.

[j cAT]

Originally Posted by 97copcar

Thanks, that testing is beyond my abilities. I'll make an appointment with my mechanic.

my guess is the cat convertersor exhaust is plugged up. the egr is part of that back pressure issue..

opti issues are missfires at the higher rpm. I would still check that coolant is not getting into it from the weep hole.

the idle issues can be PCV or hoses to and part of the crankcase venting system.

the IAC in the throttle body needs periodic cleaning and the passage ways to insure a smooth correct idle.


96 impala ss LT1 .....

[97copcar]

Thanks, I look at that stuff this weekend. That is stuff I feel confident I can check.