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Discussion Starter #1
Hi all,

My oil light indicator in the dash just started blinking kind of erratically the other day on my '97 STS.

After the engine/oil warms up, at stoplights/stopsigns etc. the engine oil light starts blinking. As soon as I take off it goes off.

The tach says the engine is idling at around 650 RPM or so. Of course if I just touch the accelerator a bit (ie. bring rpm up to 700-800 or more -I don't know how accurate the tach is- the light goes off.

The current oil level is about 1/2 way between ADD and FULL. The oil has less than 1000 mile on it since changed.

This just began happening for no apparent reason (ie. I haven't driven it any different or done anything to it for the past 3-4,000 miles.


I suspect one of three things. Can anyone suggest any more?

1) The idle is too low (the needle is just above the center tick of ticks between 0 and 1000 RPM.

2) The oil pressure senor might be failing (or has suddenly become too sensitive).

3) The throttle body plate (not sure of that term) needs cleaning.

What do you think I should look at?

Is there a diagnostic procedure I can run that displays the oil pressure in real time? What is the range it should be within? How do you run the procedure?

If you agree that its consideration 1), do you know the procedure for raising the idle a bit?

Thanks for your comments & thoughts in advance! :)

..rickko..
 

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Have you checked your diagnostic codes...... Check it at idle and see if you get a code......

I really dont know, so ill leave this one to the other people!!!
 

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Same exact problem!

I am experiencing the same exact problem with the 1997 Eldorado that I just bought. I can't figure it out. Like you said, it doesn't happen until the car heats up and then it only happens when the tach falls below one, usually at stop signs and red lights. Occassionally it happens on hills and grades also. As soon as you hit the accelerator the light goes off. I'm baffled by this. What's even more baffling is that I took it to get the diagnostics checked and nothing came up! Where do I turn now? Any information would be great! Thanks!
 

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Re: Same exact problem!

Have a mechanic temporarily install a "mechanical" oil pressure gauge and compare to the spec for your engine.
There are a few things that could cause this but the first step would be to verify the low pressure condition.
 

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Discussion Starter #5
Anyone know what RPM a '97 should idle at? Do you also know how to adjust it?

Thanks,

..rickko..
 

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If the idle is too high/low, that means something is wrong..... You dont want to just change an idle screw, because if everything is in good condition then you wont have to adjust the idle...... Check for intake cleanliness, and spray the MAFS with brake parts cleaner...... That should give you a start.....
 

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Discussion Starter #7
elwesso said:
If the idle is too high/low, that means something is wrong..... You dont want to just change an idle screw, because if everything is in good condition then you wont have to adjust the idle...... Check for intake cleanliness, and spray the MAFS with brake parts cleaner...... That should give you a start.....
Thanks for the advice.

I have brake parst cleaner but what's an MAFS and how visible is it? I have an Allante Service Manual which covers the '93 Northstar. Do you suppose they use the same termonology?

I agree with you, something is probably getting a little dirty over time and needs cleaning as the idle (I believe) is probably too low- I just don't know what it should be though.

..rickko..
 

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MAFS-- Mass Air Flow Sensor...... The pre 96 (pre OBDII) didnt have one, so you wont be able to use the allante manual for that!

<i cant say exactly where it is>, but somewhere along the intake tract before the TB you should see a wire coming from the tract..... Connected to that should be the MAFS...... Undo the closer end of the hose and douse it with brake parts cleaner.... Let it air out, and repeat a couple times.... Make sure its dry before restarting, or you could cause a fire!

Usually the idle will be somewhere around the 650 or 750 area, but I dont know for sure........
 

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The idle is computer controlled and therefore it varies. If the idle is low, there's a reason for it like the IAC is out of spec, or the TB and or IAC could be cruded up with carbon.
The MAF is usually located just inboard of the filter housing. Be VERY careful when cleaning it and you SHOULD use a product meant for it like throttle body cleaner or carb cleaner.
 

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DEFINITELY dont touch the element, unless you want to just get a new MAFS.....

Brake/electrical parts cleaner has worked good for me.....

You might just try running a can of TOP ENGINE CLEANER, available at any GM dealer, through it and see if it clears anything up.... Like 7 or 8 for can, and it does a good job......
 

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Blinking oil light...

Rickko, try changing the oil. The light will flash when the pressure is low. The lowest point is at idle. 650 is correct for a NorhStar. The computer controls the idle so don't mess with it unless there are othe probs same for the MAF. How many miles are on this vehicle? Could be wearing out, wrong viscosity oil, short to ground???? Mechanical oil pressure guage is the only way to verify the condition.
 

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Discussion Starter #12
Re: Blinking oil light...

Axle said:
Rickko, try changing the oil. The light will flash when the pressure is low. The lowest point is at idle. 650 is correct for a NorhStar. The computer controls the idle so don't mess with it unless there are othe probs same for the MAF. How many miles are on this vehicle? Could be wearing out, wrong viscosity oil, short to ground???? Mechanical oil pressure guage is the only way to verify the condition.
Miles on vehicle: 77,000
Oil changed at 75,000 plus one quart added since change.
Viscosity 10-30w
Short to ground. I hope not.
Mech. pressure gauge. I suspect the oil pressure can be read via the diagnostics. I just don't know how to cycle them to where Oil Pressure is displayed.


This is kind of a follow-up on this topic. Yesterday I noticed the light was coming on more often around idle. Then the chime bell rang and my info.console.display said, "STOP ENGINE". This was at idle while waiting for a green light.

Instead of stopping the engine I revved up the idle to about 800 rpm. Still got flickering Oil Indicator. Revved it a bit more and it disappeared.

Of course, while underway the Indicator never came on.

I considered driving into a dealership but thought i better do the simple thing first and check the oil level. When I got home I checked and found the car to be down about 1 1/2 qts. I topped it off and haven't seen the Oil Indicator flash since.

My conclusion: Apparently the oil pressure sensor is quite sensitive to how much oil is in the crankcase.

I'm going to keep a close eye on this.

Anyone use that "High Mileage" oil being marketed by various companies now? I wonder how it holds up in these North* engines.

..rickko..
 

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Re: Blinking oil light...

rickko said:
Miles on vehicle: 77,000
Oil changed at 75,000 plus one quart added since change.
Viscosity 10-30w
Short to ground. I hope not.
Mech. pressure gauge. I suspect the oil pressure can be read via the diagnostics. I just don't know how to cycle them to where Oil Pressure is displayed.


This is kind of a follow-up on this topic. Yesterday I noticed the light was coming on more often around idle. Then the chime bell rang and my info.console.display said, "STOP ENGINE". This was at idle while waiting for a green light.

Instead of stopping the engine I revved up the idle to about 800 rpm. Still got flickering Oil Indicator. Revved it a bit more and it disappeared.

Of course, while underway the Indicator never came on.

I considered driving into a dealership but thought i better do the simple thing first and check the oil level. When I got home I checked and found the car to be down about 1 1/2 qts. I topped it off and haven't seen the Oil Indicator flash since.

My conclusion: Apparently the oil pressure sensor is quite sensitive to how much oil is in the crankcase.

I'm going to keep a close eye on this.

Anyone use that "High Mileage" oil being marketed by various companies now? I wonder how it holds up in these North* engines.

..rickko..


My 96 Deville just started doing this. Initially, it was a blinking oil light when idling. Now the low oil pressure warning comes on. It immediately clears up when I accelerate. I took the car to the Cadillac dealer and the mechanic tells me they don't know what causes this. He THINKS he has atheory and can fix it, but it is a major job (around $2000) and no guarantees. Anyone have any other guidance? For now, I'm driving and just giving it gas when the warning comes on.
 

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Discussion Starter #14
Re: Blinking oil light...

Another followup since my last post about topping off the oil fixing the problem.

I drive mostly in the San Diego area, a fairly temperate climate.

Even with oil level at Full on the dipstick I've seen this problem re-occur. The circumstances are; hot day, lots of city driving, air conditioner on.

The light comes on with the a/c compressor; which happens to lower the idle JUST ENOUGH when it kicks in. When the compressor goes off, no light at idle.

I think its a matter of idle to low which may be most affected by dirty throttle plate (just a guess though). So, one of these days when I get a discount coupon mailer from my dealer I'll probably take the car in for their cleaning service.

Also, as soon as I use up my current supply of Penn. 10-30W oil I have in my garage I'm going to try an oil change using the High Mileage oil to see what affect that might have.

..rickko..
 

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From what you were saying in your last post about the heat and the AC compressor Im thinking that maybe you should get your rad flushed. There might be some gunk in the trans coolant line that is restricting the flow and causing things to heat up.
I had a dodge that started off with the same kind of signs. Temp lights, oil lights, engine lights and no explainable reason why.
Eventually I came off the highway and ended up with nothing but first gear.
Had the tranny rebuilt but it was the same thing over and over. The car was in and out of that shop at least once a month for 6 months.
Gave the car to a friend of mine who had it looked at by a friend of his and he found that the trans coolant line was plugged. Things were slowly heating up which caused the different warning lights until it finally plugged right up and burned out the tranny
Apparently the tran shop I had it at didnt see that!!!

I know its nowhere near the same kid of car, but thought that I would mention it anyways.
 

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Flushing the radiator wont help the clogged tranny heat exchanger line!!

What the heat exchanger is a tube that runs inside the radiator containing the ATF...... That line needs to be cleaned seperately..... Thats why on a lot of newer cars they have a filter just before the heat exchanger-- to minimize cloggin like this!
 

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Thanx Wes thats good to know.
Another bit of info to add to the grey matter.
Im sure it will help in the future. :yup:
 

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Discussion Starter #18 (Edited)
Here is the latest in this saga.

When I started this thread the car had 77k on it. Wednesday I took it into the dealership for its 90k service. This is the first time I've had 'professionals' touch the car other than a throttle body cleaning since I bought it with 72k miles on it.

OK, as I just said, a few months ago I thought I'd have the throttlebody cleaned 'cuz I got a coupon in the mail. Thought that might raise the idle enough to stop the light from occasionally flickering. As it turned out, it didn't. All symptoms remained the same as I originally described them.

Now lets get to Wednesday/Thursday (9/16/4). I picked up the car after their service and found as soon as it heated up the light started flickering again. The only difference, now it stayed on more than flickered. Again, A/C on, and at idle.

Oh, I forgot to mention in the off chance the problem might have been the oil pressure sensor (OPS) I had it changed out; $12 part, $110 labor!!!! Oh well....

Since I just picked up the car and only put about 7 miles on it at this point I drove it back to the service manager. They kept it overnight and called me this morning.

1st, at their expense they put in another new OPS. Symptoms remained the same.

Then they said, "Well, its either mechanical or electrical." I figured since the whole damn car runs on a computer, the chances are better that they'd find an electrical problem so I gave 'em permission to test the electronics ($102.00).

Late this morning I got called back to tell me the electronics were fine! No problems except when they tested the fuel gauge circuit the needle wavered from empty to full (it doesn't do that without the test equipment hooked up and running, only when it is hooked up).

The suspicion they voiced in regards to the gas gauge was (in so many words) that the instrument panel may be starting to go bad.

Back to the oil light problem. They said, "Electrics are fine. Its obviously a mechanical problem. That will take an engine disassembly to determine and fix the problem." They went on to say, "With the car on the lift, engine idling, there is an obvious 'clattering' sound coming from the oil pan area. Above idle it disappears.

Here's what I told them. "I'll live with the light flicker." If its mechanical and requires a teardown, then I'll drive it till it REALLY requires a teardown, or new engine.

So, thats where I ended up with this problem.

My opinion is, if you have the same problem, learn to live with it and enjoy the car. Ignore it as long as it always goes off once the car is revved off idle.

I am going to try one more thing which mentioned earlier but never did try, I'm going to run that High Mileage oil in it at the next oil change to see if that has any affect. Whether it does or not, I'll report it here!

Oh, if anyone with this same problem has converted over to the High Mileage oil and seen the problem subside or go away completely, let me know!

Lastly, one more thing came to mind. I've always run Pennzoil 10w-30 in the car. The dealership put in Castrol 10w-30. Maybe there is enough difference between the two brands that is the reason the light stays on more steady than it ever did with Pennzoil. Or, the new sensor is really more precise than the old one. Just more thoughts to ponder.

Oh, total cost for all this "investigation."

Throttle Body Cleaning 92.66
New sensor Installation 149.82
Electrical circuit checkup 102.00

Total! About $350.00! All to try and eliminate the light from flickering on the dash. I hope my experience, and money, helps you save your own money.
Please send contributions to..... hahhahaha :)

..rickko..
 

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Hey rickko, first off is do you do your own oil/filter changes or have it done? Next suggestion is to use Castrol or Valvilne 10-w30 and replace one of the 7 qts of oil for 1 qt of LUCAS Engine Oil Stabilazor, stuff is about $8 for a qt. but it should help. This stuff does a good job as I was having similar problems with my 89 Deville and that cured the oil pressure light from flickering (in my case it turned out that it was the oil sending unit/switch).
 

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Discussion Starter #20
AElayyat,

I don't think you read my last post correctly. The dealership used Castrol 10w-30 instead of what I use (when I change my own oil), Pennzoil 10w-30.

It sounds like your switch is similar to what is called an Oil Pressure Sensor on a Northstar. In my case, the original and two NEW ones all seemed to give the same response; a flickering oil pressure light at idle w/AC on while car is in Drive.

Since my engine has a tendancy to run through a qt. of oil every 800-1000 miles I will be adding something at that time. Probably will try 1qt of the high mileage stuff first. Then repeat at each successive 1k oil-add points.

Thanks for your suggestion.

..rickko..
 
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