my oil pressure light comes on at idle?

701 Views 24 Replies 8 Participants Last post by rob, Nov 18, 2001

rob

Discussion Starter · Oct 31, 2001

i noticed it last week, figured the idle was set too low so i bumped up the idle a little bit, i took it from 650-700 to 800+, the light still comes on occassionally, when at idle, i also notice that when the light is on the oil pressure gauge is 1 tick below the big tickin the middle, does that make sense? once i give it gas the ligt turns off, but at the same time the oil pressure goes up so my questions are....

should i bump up the idle a little more? if so how much?
do u think my oil pump is going bad?

1 - 20 of 25 Posts

WICKEDDREW

· #2 · Oct 31, 2001

check your oil

try a different weight/type of oil

check your oil pressure switch

change your oil pump

raising your idle will NOT correct the problem, it'll just hide it.

rob

Discussion Starter · #3 · Oct 31, 2001

i use amsoil 20w50, amsoil filter, just changed it a couple days ago, no difference, light still comes on. where is my oil pressure switch? how much of a pian is it going to be to change an oil pump? i guess easier than rebiulding an engine

ncavig

· #4 · Oct 31, 2001

It has nothing ot do with your oil. I had the same problem with my 91 SL after it's engine transplant. All you have to do is tighten a screw to raise your idle oil pressure. Theguy at the garage did it for me so I cant help ya on how to do it. But it took him like 1 minute. He screwed it in then checked to make sure the light didnt go on anymore.

WICKEDDREW

· #5 · Oct 31, 2001

That doesn't repair the CAUSE of the low oil pressure, though. I would think he'd rather fix his problem than hide it.

stealthII

· #6 · Oct 31, 2001

Your oil is plenty thick enough to have the oil pressure raised, so that's not your problem, the idle control will just mask your problem, it will come back again. Have you added any additives in your oil?? The reason I ask this is because I added ATF to my oil and it clogged my oil pump. Might want to check the oil pump.
Rich

WICKEDDREW

· #7 · Oct 31, 2001

Richie---How did ATF clog your oil pump? It's made of a 5 weight base oil, and it has the same additives as motor oil: seal swell, friction modifiers, and detergents, and it has no polyalphaolefins or synthetic hydrocarbons to gunk up your engine.

G

· #8 · Oct 31, 2001

I've been having the same problem for about 2 years now. The gauge shows normal but the light will come on occasionally at idle. From previous posts in this group (a year or 2 ago), I decided it's nothing to worry about (other people had the same problem). Most probably a bad sender switch for the light.

Elmo

· #9 · Oct 31, 2001

Oh boy. Here we go again. Don't let Matt92VR4 see this thread.

(Hi Matt!

)

There are TWO oil pressure signal devices on th DOHC version of this car. Look at this diagram for oil circuit inside our engine. It will help you to understand how the oil circulates.

<img src="http://wsphotofews.excite.com/032/ba/ic/O8/T127507.jpg" alt="Oil Paths for a DOHC 6g72" alt="DOHC Oil Diagram">

The oil will go from the pump, into the filter, and then upwards toward the engine. From there, it passes two signal units, first, the oil pressure gauge unit, which measures oil pressure by varying resistance to the 12 volt signal being fed to it before dumping the voltage to the engine block (Electrical Ground). This is how your oil pressure gauge works, it measures carefully, the amount of electrical flow passing through it (which ultimately goes through the gauge unit, and then into the block)The second, is the oil pressure switch unit, which is an electrical switch; when the pressure falls below a certain level, it closes the loop, and allows that 12V signal to ground, thus turning on your Oil light on the dash.

SO, here's the skinny. If for some reason, your oil light is coming on, then that unit (the second one) is thinking the pressure is too low. This can happen for three reasons off the top of my head:

1) the oil pressure switch unit itself is dying. this allows voltage to flow through even when the pressure is decent.

2) the oil itself is breaking down, and can't hold thermal viscosity. When oil gets burnt up too much, it has this wierd property where it flows too easily, because the additives to prevent thermal viscosity breakdown are gone.(burnt up into residue) This makes the oil thin at running temp, and thus, lowers overall pressure. Quick way to check this, change your oil. Put fresh 10W-40 in, and see what happens (10W-40 depending upon your location. If you are in a warm climate, use 20W-50) Part of this is also due to the fact that the oil picks up other contaminents from being circulated, like other oils, things not burnt off in the fuel, and possibly seeping fuel components that mix into the oil.

3) Your oil pump is bad. This requires a replacement. About 170, plus labor to dig it out. (this is akin to a timing belt job, since the oil pump is right under the main crank sprocket for the timing belt.) it will also require removal of the oil pan, since the pick up tube needs to be accessed also.

That's the nuts and bolts of it. Post if you have questions, I'd be happy to answer them.

Elton

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rob

Discussion Starter · #10 · Oct 31, 2001

no i havent added any additives, just 20w50 amsoil for the past 7 changes or so. i dont think the oil is breaking down already, it was just changed not too long ago, should i replace the sensor? where is it? how much? how many beers will it take me to get to it? i have changed my fuel on the safc to add more fuel at idle to keep the idle rpm's up a bit, its at -23% now with 460cc's, didin't help too much. oh also im in michigan, do u think the 20w50 is too thick? should i rechange the oil and put in mobil 1 10/30-40? thanks for any help

maTT

· #11 · Oct 31, 2001

oil pressure? whats oil pressure???

j/k

I would change the switch and sending unit. They are ver easy to change. I would say an hours tops for both of them including cleanup and beer time. I would also run a thinner oil.

Rob, once again congradulations for having the best looking 3s car (in my opinion). I hope to see it at ocean city or th eshootout this year

How is it running? How much boost you running?

Elmo

· #12 · Oct 31, 2001 (Edited)

rob said:
no i havent added any additives, just 20w50 amsoil for the past 7 changes or so. i dont think the oil is breaking down already, it was just changed not too long ago, should i replace the sensor? where is it? how much? how many beers will it take me to get to it? i have changed my fuel on the safc to add more fuel at idle to keep the idle rpm's up a bit, its at -23% now with 460cc's, didin't help too much. oh also im in michigan, do u think the 20w50 is too thick? should i rechange the oil and put in mobil 1 10/30-40? thanks for any help

Too thick? Doubt it. If thickness were your problem, your pressure would be reading unusually HIGH, not LOW.

If the oil is fresh, maybe try another brand. If that still doesn't cut it, then yeah, spend the 50 bucks (each unit is about $20 each, while you're down there draining the oil, you might as well do both) and replace the sending unit, and the switch unit.

Jeff has a great article on his site that details where the two are located; the gauge unit looks like a little bell, with a wire coming out of it, and the switch unit, looks sorta like a fat sparkplug. It goes into a 'Y' block, where one tap is for the switch, and the other goes off to feed the rear Turbo. (be careful around that line, it's only $20, but if you crack it, it will bleed oil..... and then starve your rear turbo.

)

The link is here:

http://www.geocities.com/lutransys/jlucius/2-oilpresloc.htm

It's easiest to get this, if you remove the drivers side wheel, and the wheel well plastic innards (the two shields that protect the accessory and P/S Belts)

With the car jacked up, the wheel removed, and these panels off, you can almost 'easily' get to the two units. (hey, I said 'almost')

Lemme know if you have any other questions...

Elton

*edit - whoops. Fixed the site link. Try it again if you didn't find the appropriate page before*

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rob

Discussion Starter · #13 · Nov 1, 2001 (Edited)

ya i should be at ocean city next year as well as the shootout, i was at both this year. ok, cool, so i get both the sensors and swap em out, i dont have to remove any belts do i? such as timing, power steering, whatever? anybody got part numbers by chance? im running ~ 7psi on the high setting and ~ 12psi on the low for the evc4, still untuned, i havent gone palmloggging since i changed out my o2 sensors about 2 weeks ago, could that have caused this??? anyways ill have to go palmlogging and see if she tunes, if not its gunna be a 700 mile trip to aam.

KD4PWH

· #14 · Nov 1, 2001 (Edited)

Here ya go man...part numbers from the CAPS program using my car as the vehicle. The oil pump p/n may be different for your 91, so double check it.

MD138993 Switch, engine oil pressure
MD133273 Gauge unit, engine oil pressure

And if that don't fix it,
MD190982 Oil pump assempbly

And since you are cool and have a kick ass car here are some prices from Rockville Mitsubishi. www.mitsupartsdirect.com

MD190982 - oil pump - $152.82
MD138993 - Switch oil press. - $12.82
MD133273 - Gauge unit, oil press. - $33.28

Good Luck Rob,

Chris

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rob

Discussion Starter · #15 · Nov 1, 2001

thank you very much, ill call concelli tomorrow and get the 25% discount

rob

Discussion Starter · #16 · Nov 1, 2001

k, ordered, anything else i should try in the meantime?

stealthII

· #17 · Nov 1, 2001

Wickeddrew

Richie---How did ATF clog your oil pump? It's made of a 5 weight base oil, and it has the same additives as motor oil: seal swell, friction modifiers, and detergents, and it has no polyalphaolefins or synthetic hydrocarbons to gunk up your engine.

Drew,
I don't know if that's the "exact" cause of the oil pump clogging, but when I did add the atf, thats when my oil pressure went down and problems started happening. I did hear that it could gunk up my engine and clog the oil pump. Don't know who I heard that from, So I am pointing the finger in that area.

So how are you doing man? Everything cool? Get your car running any faster @ the track? Talk to you later,
Richie

rob

Discussion Starter · #18 · Nov 3, 2001 (Edited)

now when i just started my car i think the oil pressure at start up isnt enough, the gauge reads 4 ticks under the middle big hash, it then stalled out, i restarted it and gave it a little gas and it started up and brought up the oil pressure on the gauge, does this mean my oil pump is taking a shit?

rob

Discussion Starter · #19 · Nov 3, 2001 (Edited)

i found that i was 1/2 quart low and she purrs much better now

KD4PWH

· #20 · Nov 3, 2001

Yea, no oil pressure is a bad thing. I just started my car to compare readings. At idle (700rpm), engine at normal operating temperature I have 4 ticks up from the bottom (2 ticks down from the middle big hash mark). I am running Mobil 1 15W50 syn.

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