Low Oil Pressure @ Idle

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  #1  
Old 09-26-07, 07:56 PM
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Low Oil Pressure @ Idle

'96 Camaro Z28, LT1, 68k miles, has good oil pressure at start-up. Engine warms, develops low oil pressure at idle. Low oil level light on dash will come on at first pressure drop and stay on. As car slows to stop, pressure will drop almost full scale, on acceleration, pressure gauge will climb to a "normal" range. Engine will stall on occasion at low speed, 10mph, (parking lots). Regular oil & filter changes, 3k miles or less. Oil is proper level, checked on level ground w/engine cold. Regular 10w30, not synthetic.

Question: Should we first look at possible timing/distributor problem? or Pull the oil pan and start checking oil pickup screen, regulator valve, and pump? Any ideas would be very helpful..
Thanks,
 
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  #2  
Old 09-26-07, 08:21 PM
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The speed of the engine will dictate the speed of the oil pump and that will dictate the initial oil pressure.
If the engine is running too slow for what ever reason then the pressure will drop and the oil light will come on.
I would find out how slow the engine is going when the car is stopped at the traffic light and compare it with specifications. The problem could be that the car needs a tune up.

Have you got a tachometer to look at on the dash to get a value of how many RPMs this engine is going when this happens.

Could you post us that RPM?
 
  #3  
Old 09-27-07, 03:10 AM
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would probably use a mechanical pressure guage to test the oil pressure for a starting point if you do find it is low once the engine is warmed up you might as well drop the pan and look for problems there, might even check out some of the main bearing clearances while your there as excessive clearances can also cause low oil pressure.
oil pressure will go up and down with rpm a little but a good pump on an engine with proper bearing clearances shouldnt have no trouble putting out atleast 15-20 psi even at a low idle speed of 500-600 rpm on a hot engine, most warning lights will not be turned on until pressure drops below 10 psi.
 
  #4  
Old 09-27-07, 12:08 PM
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You should do what the first 2 post say, check engine idle speed to be sure it is correct. If still low use a mechanical oil gauge. If mechanical gauge shows low psi at correct idle then yes remove the pan and check clearance on bearings. Another thing to check while pan is off is the oil pump spring. Chevy has a spring inside that regulates the pressure, thats what makes it a high volume pump or regular pump. differnt color springs give different psi. only thing you can't check is the cam bearing clearence.
 
  #5  
Old 10-02-07, 10:19 AM
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RPM's about 500 before engine stalls, oil pressure gauge will
become erratic, bounce up and down about then also,

thanks for the ideas on where to start troubleshooting,,
 
  #6  
Old 10-03-07, 08:54 AM
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Some GM vehicles have a secondary fuel pump relay tied to the oil pressure sensor. If oil pressure drops too low, the fuel pump shuts off and the engine stops. They did this on some mid 80's cars, not sure if they are still doing it or not.
 
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