Hey there,
I am really hoping someone might be able to help. I have a 89 Z24 with a 2.8L. When I start the car up the oil pressure guage reads 40. Once the car is warmed up and rolling down the road the pressure starts to drop. At a stop light idling, the oil pressure guage drops to 0. When i take off, the pressure will bounce back up around 20, but the farther I drive or the longer I am on the road, the lower it bounces back up. If I am in traffic more than 30 mins, the guage barely bounce back up, if at all. I let the car sit over night and changed the oil and filter, with no change. Any idea's??

Ok, I guess my problem has everyone just as stumped as I am. Tommorrow I am going to drop the oil pan and clean it out real good. I also plan to clean the pick up screens and hope that fixes it. I am figuring it is a clog and I have not got the gunk out simply by changing the oil and filter. It has been suggested to run seafoam thru the system to help clean it out. Any thoughts?? A family member also suggested a old remedy of running diesel fuel thru the system too. Just long enough to warm the engine up, then drain it hot and replace the filter and oil. If any one has any ideas, thoughts or comments I would love to hear them.

Well just an update if you want to call it that. Due to the holidays and time, I have not been able to work on my car. I am hoping to work on it before I have to start driving it again. I spent some time and went thru a lot of older posts. I think I have found some sound advice in posts from other people with similar problems. I guess I am on the right track. If anyone has any opions on my problem and wants to add there advice please feel free. I understand this is a busy season and you can not always find the time to help out. I hope everyone has a safe New Year and I will post again when things change.

My toughts about this hmmm. I`m guessing the engine has got alot of miles on it .If the car has been serviced properly over the years I can`t see why there would be "gunk " in the engine. Running any any types of cleaners thru it will do just that .clean out the rings etc and then you will probably notice you will be burning more oil as the oil will by pass the rings easier and go up into the combustion chamber.Rod bearings and main bearings may be worn and as it warms up oil thins. I do beleive if it`s a high mileage engine ,there is oil available for it Quaker state I think,or change the oil and throw some STP oil treatment into it and see if it helps abit. Maybe the pump is getting weak. I doubt if the pick up is blocking as you say the pressure is there when you first start It. This is just my opinion

Muff34. Thank-you for the post. I figured running cleaners thru the engine would do more harm than good. Yes the engine is high in miles and has never been rebuilt as far as I know. The car is just shy of 137,000 but runs great. Has a little tick when first started up, but in my exsperience that is common. It does not burn or leak anything. The car is great, just old and starting to cry for more attention. It has been well serviced from what I know and seen. I wanted to restore it but the car is from the north and I am not sure it would be worth the time and money. I changed the oil with a highmilage 5w-30. Since I live in Florida and cold isnt a real problem I thought about going to a thicker oil. The thought that the oil was to thin crossed my mind. I just figured since I was going to change the oil and filter again, that I would take off the pan and check things out. I guess I was hoping I would get lucky, besides you have to start somewhere when troubleshotting a problem that has you stumped. My next move I guess would have to be rebuild the oil pump or replace the sending unit. From the old posts that I read on this site it seems to be the next logical steps. Thank you for the post muff34 and if anyone else out there has some wisdom to pass on please feel free. Happy New Year everyone. :smokin:

I have a question. When you come to a stop light and idle and the oil pressure goes down to 0. Does the engine start to knock real loud? Or, even seem to start ticking a lot?

before you start tearing things apart maybe get pressure checked using a mechanical gauge just to confirm low oil press.

before you start tearing things apart maybe get pressure checked using a mechanical gauge just to confirm low oil press.

Yeah... that was my idea on it. May just be a bad sending unit, or gauge.

PulledOverAgain the car makes no noise when I am at a light. Not that I can hear. I am not sure if I have just avoided any damage yet though. You are right muff34 I don't want to start tearing the car apart and replacing parts just to see if it fixes it. Replacing parts that are not broke can get to costly. As soon as I can get my hands on a gauge I plan on checking it out. I just might have to go buy one. I was thinking of taking it into one of those skill trade centers and have them check the car out. Not sure if there is one around here. It is real cheap if not free most of the time. I use to attend one in high school. I have never ran into this problem before. Either you have pressure, low pressure or no pressure. I have driven the car more times than I problably should have and it has never changed. Good pressure when you first start up and warm up. Then as the car gets hot and the oil heats up the pressure hits 0 at idle and around 20 when the rpm's go above 2 grand. The longer you drive it the lower the pressure dips. It never changes. I have only read one thread that had a problem like mine, but the result was never posted. It turned into a pissing match for a bit, but there was some good advice if you read between the posts. I know you suggested the sending unit then Muff34 and I am hoping it is that simple. I will make sure to post my results and let everyone know what worked and didn't work. For now a simple filter and fluid change did not work. Here is the thread, if anyone is interested in reading it. Till next time. Be safe tonight.
http://www.automotiveforums.com/vbulletin/showthread.php?t=516783&highlight=low+oil+pressure

here`s some info to read up on http://www.aa1car.com/library/us1097.htm hope it helps
Happy New year
Muff

Typical symptom of worn out cam bearings. Good pressure cold, low pressure hot. If your hearing lifter noise and no actual knock in the bottom of the block, thats probably what it is. cam/lifters.

T

Wow what a coincidence.
Mine does the EXACT same thing.
I could start it right up in the morning and the Oil Pressure will be around 4.0
Then while i drive it and Idle it at stop lights it lowers and then sometimes it gets so low that the car dies and i have to start it again.

Exactly why i came to this forum aswell.

If you find out how to fix this please forward a diagnosis to me.

Im looking into this more too.

I love my car and i actually love it so much that im willing to rebuild the entire engine. Its a great car.

Then while i drive it and Idle it at stop lights it lowers and then sometimes it gets so low that the car dies and i have to start it again.

That sounds like the ECU is seeing the pressure drop. If it gets down far enough, the ECU should turn off the fuel pump.

Hi everyone!

As someone who has owned three GM vehicles with 2.8L V6 engines, (two carburated and one fuel-injected) I can say also that you need to look at your OIL PUMP. 2.8s are NOTORIOUS for oil pump failures, my third 2.8L vehicle was a 1985 S-10 Blazer and with a new crate motor in it the engine had 60 PSI during a cold start, 40 when hot and idling.

And the second car (my mother's 1987 Pontiac 6000 S/E) had that problem for four years, until the camshaft broke, and the used motor we put in also had the same problem. The sending unit in this case was fine, both oil pumps were not.

Just my two cents. :2cents:

2.8s suck

Sorry it has been so long since I posted. The good news is, I no longer have a oil pressure problem. The bad news is the car is totaled. I stopped driving it, but decided to take it on base to the auto hobby shop. They have all the tools I needed to check it out. On my way to base a moron decided to turn right in front of me. He was driving a F-250 4x4 and of course my car lost. He was cited for failure to yeild right of way, but I am sure I will not see much for the car. I am not sure how to post pics, but it might be to gruesome for some of the readers anyways. The car is toast. Now I just have to wait and see what the insurance companies work out. I would like to thank everyone for their help. I am sure with the knowledge you all shared I would have been able to fix the problem. 89Z24 RIP:disappoin

well who knows ,wrecked may be a blessing in disguise as long as no one was hurt. The car may have turned out to be a money pit(not knocking your Car). been down that road with older vehicles and it was steady nickel and dime stuff to repair. good luck and if we could see some pics that would be cool