Whenever my RPMs drop below 1000 on my 91 LX 5.0L I get a sharp drop off in oil pressure. Basically the gauge drops right down to "L." I notice it when I am stopped or driving very slow with it in either drive or reverse. If I am stopped and put it in neuteral it brings the RPMs back up above 1000 and the oil pressure shoots back up to normal. I am not 100% sure that the gauge is accurate b/c I only bought the car a few months ago. It has been doing this for a while now and at first I thought it was a faulty gauge b/c it seemed to be moving around so much but when I took a closer look I could see the pattern I just described. The pressure is fine when I am just crusing along.
Is it definatly my oil pump or could it be something a little easier to fix, possibly the sender or the gauge? Please let me know what you guys think it might be.
I would consider replacing the oil pressure sending unit or hooking up a mechanical gauge temporarily to see what is really going on. The oil pressure sending unit is threaded into a pipe that threads into the oil passage on the drivers side of the motor. I wouldn't drive it until you find out what's going on because a bad oil pump / worn oil pump driveshaft can cause serious motor damage if you have inadequate oil pressure.
If you replace the pump, DO NOT use a high volume pump no matter what the part store or mechanic recommends.
Ok, I will do that as soon as I can. Its been like this for a while now but I just noticed the pattern. I wrote it off as a bad gauge at first which was probably really dumb on my part but now I want to get it right.
Also...if I replace the sending unit do I need to drain the oil first? For instance if I try to do it with the oil in will it drain out through hole the sending unit sits in?
yes that is where it is. i would not waste any time at replacing it. if you still have your problem you need to get a mechanical gauge and verify that your not getting appropriate pressure. if your pump is bad you need to fix it ASAP. driving with a bad pump is very very bad...
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13.4@106mph (on old 302, no ET's on stroker yet)
'94 GT 347 Stroker, TFS stage 2 cam (.542 lift), AFR 185 heads, Edelbrock Performer RPM intake, 30 lb injectors, 77mm Pro-M, Fox Accufab 75mm Throttle Body, 255lph fuel pump, Mac fox style Long Tube headers, Tremec TKO, aluminum driveshaft, 3.73 gears , Flowmaster 2 chamber, chrome Cobra R 17x9's, Steeda radiator, Eibach Sportline springs, Tweecer RT
My first guess would be the sender, and don't buy a cheap one. They never work right.
My second guess could be your bearings are toast. Get someone to do a compression/leak down on the motor to see if your compression is still good. It's usually the passenger side of the 302 block that gets warmer and has issues with torn headgaskets, etc. Then start replacing parts as needed.
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"Mad" Max
1992 LX, thanks to Chicane Sport Tuning and some friends.. it is now wrapped with new graphics and ready to hit the streets AGAIN!!!!
yea my oil pressure use to run at the (o) when i got it about a year ago now it runs at the (R) anybody got any ideas and no it aint smoking so i dont think its the rings
If you can borrow a buddies unit, trade it out and see if you get the same reading. Make sure all the connections are good as well before swapping it out... Is it electrical or mechanical?
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"Mad" Max
1992 LX, thanks to Chicane Sport Tuning and some friends.. it is now wrapped with new graphics and ready to hit the streets AGAIN!!!!
drop in oil pressure so small like that can also be caused by a different filter or different weight oil, i always run 20W-50 and have had 3 302's go over 200k so im sticking with it
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1989 Ford Mustang LX Notchback,5.0L 5 speed
331 Stroker wuth forged eagle rotater, Scorpion roller rockers, mahle forged pistons, AFR185s,Spec Stage 2+ Clutch,Steeda Sub Frame Connectors with Seat supports,Hurst Short Throw Shifter, Mr. Gasket Hi0-Flo 180* T-Stat,Lunati VooDoo Series cam,Trickflow upper and lower intake,BBK CAI,BBK Long Tube Headers,BBK Off-Road H-Pipe,Flowmaster 40 Series Mufflers,Aluminum Driveshaft,17" Cobra R's,10000K HID's One problem after the next !!
Oil pressure problem, please help. 
anybody got any ideas and no it aint smoking so i dont think its the rings
