Question about 1991 Pontiac Grand Prix

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Oil pressure wont stay up in my 3.1 V6

Ive replaced my oilpressure switch and the wireing to it and ive looked for leaks and cant find any when the engine is cold the presuure stays up but when it warms up if i dont keep my foot on the gas (like if im stopping at a red light or stop sign) the pressure drops and sometimes goes low enough to kill the engine(the engine dies due to a safety feature in the engine so it doesn't ruin the engine) but once i press the gas it goes back up

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  • dvoraklj Nov 29, 2008

    sofar on oil ive tried 5w and 10w but i havent checked any filters other then the oil filter which was changed 200 miles ago the oil did feel sandy and was thick but i just placed that with the fact that it was old oil and the car was sitting for a few months while i replaced some wires leading to other sensors, im in nebraska so the temerature is always different and i was told to try a 50w by one of my friends but then it would be harder on the engine during the winter since i dont have a garage to keep it in

  • dvoraklj Dec 04, 2008

    that was what i thought when he told me to use the 50w and ill look up the oil pump aswell thanks

  • Wayne Mineard
    Wayne Mineard May 11, 2010

    No way you should be using 50W in that car!

    Multi-viscosity 5W30 or 10W30.

  • Wayne Mineard
    Wayne Mineard May 11, 2010

    Sounds like you may be looking at replacing the oil pump.



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The pump filter screen is probably partly stopped up. when did you last change the filter itself?
on the pump,there is a filter screen (not the filter) that is used to keep large items from getting sucked into the pump which is located on the of the engine submerged into the oil in the oil pan.
the oinly way i know to unclog it without removing the oil pan to access the screen, would be to drop the pan low enough to get to the screen with an air line to try and blow the trash off.
it may be possible to use a reversing drill motor to run the pump backwards to try to clear the screen, but i'm not sure if that is possible on your vehicle.
someone else may have another solution.
one other thing may also cause the low pressure drop. that is the oil viscosity. what oil are you using? 30w doesn't have the same viscosity as 50w. also, 5w30 and 10w40 have varied viscosity from high to low depending on engine temperature. high viscosity is thinner for higher temps, low viscosity is thicker for lower engine temps. the oil you use may need to be of a higher viscosity if you live in a cooler climate, and lower if in a warmer climate.

Posted on Nov 27, 2008


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