I have a question that I am not finding adequately answered in the stickies.
I figure some of you might know the answer..so here goes.

After my car warms up and I drive it for a while, the oil light will come on when it's sitting at idle. It will go back off when I start moving again, sometimes it goes off at ~1000rpm sometimes ~2500rpm.

I thought maybe it was because I left the oil filter on there longer than I usually do, but I changed both yesterday and the same thing still happens.

I assume it may be a problem with the oil pressure sensor which is a easily to replace part. I use Mobil 1 and certainly change the oil within the 7500 miles that the oil is supposedly good for.
The only other reason I could see this happening is my idle is a smidge lower than maybe it should be ~700 or a little lower.
What is more likely a bad oil sensor or low idle? Either one is fairly easy, but I didn't want to climb under there again unless I have to (until the next oil change anyway).
There is nothing else that could be wrong, could there?
I did have the rear valve cover gasket leaking for a time (which is what I thought might be causing the oil pressure light to come on). I fixed that however, and the same thing continues. There is oil around the area, but I am not sure whether it's from the valve cover I let go for a while, the fact that I don't always clean the area where I change the oil filter, or that it's actually leaking.
Could the residual oil just be causing a bad connection?
I would greatly appreciate any advice anyone can give me, I am not as familar with cylinder engines being that I owned a 82 RX-7 for 9 years.

 

Assuming the oil level is fine - it's just a bad sending unit.

 

Hopefully its the sending unit, if not then possibly the oil pump.

 

But highly unlikely.

 

It behaved the same immediately after I put 4.25 quarts of Mobil 1 in yesterday.
I posted this thread because if there was any telltale signs of something I don't know about, I figure someone on the org would catch it.

Thanks to you all.

 

I would put money on it .... Oil light is relative to oil pressure, rather than level, from your post, I'm sure you knew that ( read: you're not a :newbie)

So, I would say unless your idle is extrememly low 200-300rpm, I would say it's the oil pressure sending unit.

This is the 5$ piece located just behind the filter area.

 

Let's not forget that badly worn rod's, mains, and a few other things can cause that to, but were talking about a vq here, so unless it has over 300k or you beat on it with really low oil it's probably the sending unit.

 

I have auto-x ed my car with this light being on when at idle. I normally drive at 80+ (because I work in NJ, where most speed limits are just really guidelines) so I was assuming that if it WAS something major (i.e. oil pump) my engine would start overheating.
And as far as beating on the vq, yes ...yes I do, but with low oil..no.

 

The oil pressure sensor is a common failure item on our cars.
You can probably be 99.99999999 % sure it's the sensor, just replace it.

 

Finally got around to changing the oil pressure sensor (only took me a year and two tries at advance auto parts to get the right part).

Anyway, I noticed two things. 1) Is that using a crescent wrench doesn't work very well. I broke the old sensors electrical connections while getting it out the first time, and then Advance auto gave me a part that I didn't like the look of, so they had another part that they could get the next day. I tried pep boys, but their part looked exactly like the one I didn't like from advance, so I just paid the $0.07 difference and had them overnight the other part.

So, in order so that I could drive the car to work, I put some RTV sealant on the broken oil pressure sensor and screwed it back in.

2) I think the oil pressure sensor must only send a signal to the idiot lights when the pressure is low, essentially a fail open sensor. Because when I hooked it back up (it seemed like it was connected, but it was questionable), the light didn't come on.

I got the right part, and since I couldn't find anywhere obvious to get a 26mm deepwell socket (ie sears, pep boys, advance auto, walmart) I looked at snap-on, but they wanted $36 for the single socket. I called a local Federated parts supplier and they had a $7 oil sensor 1/2 inch drive sprocket that had multiple levels in it for 2-3 different sizes.

So, I put the new one in, and no idiot light comes on, and away I went, but now I'm thinking it must be a fail open circuit. Meaning that if the sensor is bad or completely disconnected, the circuit won't close and the light won't come on.

I did leak a little oil while changing this sensor, but I jacked up the back of the car on stands to minimze the spilling. And it's not like I can tell how much oil I lost since the vq dipsticks are the most useless pieces of $hit I've ever dealt with on any car.

 

So, explain how the circuit will close if it were indeed fail safe? Kill oil pressure, or kill the engine (in a sense of fail safe, shut off, fuel cut etc)

 

Your Car Needs Oil!!!!!

 

Have you tried letting it sit for about 10 min, warm, without the dipstick in? I'm not able to get any useful reading at all unless I do that.


Low oil pressure doesn't mean the same thing as low oil level.

 

 

no, no not fail safe. I'm just talking about the circuit itself.

What I mean is that if the sensor "senses" a low oil pressure, it closes (ie connects) the circuit and your oil light comes on.

Since when I put the broken sensor back in, and no light came on, I am guessing that it's a fail open (disconnected) sensor.

My old sensor probably was actively failing, as the light would come on and off sometimes randomly, at first it seemed like it was related to the rpms.

So, now I have a new sensor in there, but what I realize is that if you disconnected your sensor, you woudn't get a light anyway.

With this in mind you might never be able to know if you
1) have your sensor disconnected
2) have a bad sensor that just fails altogether
3) actually have low oil pressure without an additionaly gauge test