Oil pressure issue

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?

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.

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?

See answers in Red.

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.

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.

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

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?

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?

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.

I think a compression check is in order.

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

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.

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

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 .....

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

97 copcar, lots of good advice here. What weight oil do you use? how many miles on your car? If it were mine I would probably go with a thicker oil probably a high mileage oil. Just don't go overboard on thickness. Good Luck.

It has some age on it at 230,000 miles. As for the weight of the oil, I use what the manual suggests, if i recall it is 10w-30.

Unfortunately my weekend was overcome by events and I was not able to look at the items suggested, hopefully I can do it later this week or this weekend.

97copcar, I've always used 5w40 in my wifes GMC since new without a problem, with your climate it wouldn't hurt at all to go slightly thicker. Good Luck.

Also sometimes the egr passages in the intake get clogged, something to look for.

It has some age on it at 230,000 miles. As for the weight of the oil, I use what the manual suggests, if i recall it is 10w-30.

Unfortunately my weekend was overcome by events and I was not able to look at the items suggested, hopefully I can do it later this week or this weekend.

with that mileage if you went too long on oil changes and also used fram type filters that allow larger particles to pass this could mean worn crank bearings. with the greater clearance you will have lower pressures at normal engine temps. at cold start pressures may appear normal. eventually the camshaft/rockers will fail.

if the oil was changed at 3-4000mi intervals and you used high quality oil filters ac delco/purolator plus/wix and the 10-30wt regular oil this should not have occured. fram filters have poor quality control.

HOLES IN THE FILTER MEDIA .

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


Read this:

http://easyautodiagnostics.com/

Sorry for the late reply here guys, i have had a ton going on at my job and it has left little time for personal stuff.

A few weeks ago the Service engine soon light came on. The code I pulled was for multiple random misfires. With all the stuff going on, my buddy suggested rebuilding the optispark. He has 3 or 4 Chevy Caprice's with the same LT1 in it.
I got the MSD rebuild kit and we installed it over the weekend. Oh my god did that wake the car up. I put some miles on it this morning and my 1,500 to 2,000 rpm stumble appears to be gone. The car is running cooler also.

I think I also found my coolant leak, looks like I need a new radiator cap. I am getting one today.

Thanks for everyone's help. If I still have nay issues I'll be sure to post up.

you problems were poor idle, loosing coolant,miss fires @1500/2000RPM
and oil pressure droping out.

so the opti was responsible for most of these issues ?

when the water pump was removed did the weep hole look stained with dexcool ? with the opti cap removed what did you see internal of the opti ? any oil/coolant evidence of carbon/arcing etc...?

was the opti cap gasket broken ?

The coolant issue is still present. I replaced the radiator cap this afternoon in hopes of it helping. I have to fill up and burp the system so I am not sure if the cap fixed it or not yet.

The opti rebuild fixed the misfires, i have not driven it enough to know if it fixed the idle/oil pressure issue. I have a feeling it did not.

The water pump was dirty, I am not sure if that was from oil spraying or dex-cool. It looked more like dried oil. I cleaned the bottom of the pump so if anything comes out I can tell.

The seals were intact and the rotor and the posts inside the cap were corroded. The test drive i did last night showed me that the power is back in the car.

The coolant issue is still present. I replaced the radiator cap this afternoon in hopes of it helping. I have to fill up and burp the system so I am not sure if the cap fixed it or not yet.

The opti rebuild fixed the misfires, i have not driven it enough to know if it fixed the idle/oil pressure issue. I have a feeling it did not.

The water pump was dirty, I am not sure if that was from oil spraying or dex-cool. It looked more like dried oil. I cleaned the bottom of the pump so if anything comes out I can tell.

The seals were intact and the rotor and the posts inside the cap were corroded. The test drive i did last night showed me that the power is back in the car.

the opti venting reduces the corrosion inside . this arcing creates gases that will damage the metal over time this is why it it important that the testing of this venting system is done every couple of years.

the coolant maybe black dirty from being too acidic. this can and does occur. when this happens replace the coolant. remove the knock sensors both sides of engine . this will drain the block. only use distilled water to make the coolant mix of 60% dexcool to 40 % distilled water.

always remove heater hoses at the block and blow out and flush out. this way the heater will produce high heat .

on the back of the block is a hose [metal] if this ls leaking it will also cause your coolant loss. not easy to get to.

I drained all of the coolant out of the water pump and radiator to do the opti and purchased the premix collant, I did not want to mess with mixing the disstilled water at my buddies house.

The heater core was repalced last year, it should not be clogged quite yet. I'll have to see about flushing it anyway just to be sure.

The work on the car just got put on hold. I had a death in the family last night and will be out of town for a few days. I may or may not be able to look at this when i get back this weekend.

For now I am driving my girlfriends car.
This car is frusting the hell out of me. When it works, it works great but, as of late it seems like I fix one thing and another goes south.

Thanks to everyone who has been helping me along my journey to fix my car. I am sure one of these days it will be fixed and no other issues found for a while*L*

I believe I found the coolant leak. It looks like there is a leak coming from a line in the water pump. It is the line with the bleeder valve in it.
I will be removing the hose, hopefully this weekend, and seeing if i can find a tear or hole. If not, I'll put it back on and run the car. Who knows, maybe I did not put the clamp on right when I did the opti rebuild.

I had the same issue. But it turned out to be a leaky headgasket. So I poured a bottle.of k&w head gasket sealer and it kinda solved the problem. I still have a low oil pressure, so Im changing the oil pressure switch and hope for the best.

I had a leaky head gasket about 7 or 8 years ago and had it replaced. While not impossible that it went bad again, right now i think it is not likely.

I found time to look at the car again and found the coolant leak. I have a pin hole on a line coming out of the water pump. It is the line with the air bleed screw in a T connector. I traced it back to some metal pipes. Is this going to be a pain to replace or is it a matter of pop a few retainer clips and pop in the new line?