mustang883

Anyone ever have this problem before?....

Stock 5.0 EFI HO in a fox body
When cold, oil pressure is absolutely fine, middle of the gauge
While driving, will fluctuate between middle of gauge and 2nd tick mark from red on bottom when warm
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HERE'S THE PROBLEM. . . .
when engine iswarmat idle, all of a sudden needle will drop right into the red,zero oil pressure(you can feel engine shutter a little too)
if you tap the gas and bring rpms back up, oil pressure returns, but as soon as you let it idle again it drops again. . .
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Tried putting thicker oil in engine (20w50) to see if it would help w/ pressure and still does the same thing
-haven't tried an engine flush yet, reluctant to pull engine to change oil pump. . .
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Is it worth trying an engine oil flush? What flush is best to use? If flush not worth doing, is there any way to change the oil pump without pulling the motor?

93 LX FiveO

engine flush?

before you go throwing money at this... buy yourself a mechanical gauge and new sending unit.

while you're at it, get one for the coolant temp.

both are notorious for giving "misleading" signals to the engines actual state of operation

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67mustang302

Yeah, get a gauge that doesn't suck. If it is actually low at idle and cruiseand the engine has miles on it, you could just put a high volume pump in it.

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Who cares how much horsepower it has, all that matters is how fast it goes!

Best run 13.23 at 106.97mph with a 2.183 60'
Times from before tune and driver mod.

slickshift

Yes, stick a real gauge on it first

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'86 GT that technically doesn't exist
With Accessory Reserve Load springs
Accessory Reserve Load Springs...Whooo Hooo!
The Last Four Eye

Grundy

very common problem for 5.0's. you can get your mechanical gauge and make sure if you want, but wheni bought my car you could HEAR it had no oil pressure, very commin for a high mi 5.0, lots of oil pressure untill you want to idle

93 LX FiveO

when i first hooked up my mechanical gauge, the oil pressure was dropping to about 22 at idle when warm.

i changed the oil, found no coolant or fragments. i used 5 quarts of 10w40 castrol gtx and 1 quart of lucas oil stabilizer

lowest reading ive gotten so far was 38 psi at idle coming off the highway after a 2 hour trip.

its an expensive oil change but it will keep the motor going longer. the lucas stuff works well in our cars.

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ZachW04Stang

Its the stock gauge don't trust it. Mine bounces around at idle and cruising steady. When I hooked a mechanical guage up, oil pressure was perfect and steady. It would probably be a good investment into a good set of aftermarket gauges.

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84 Mustang SVO
86 Mustang GT
http://www.youtube.com/86zach

drhoward

Hey sorry to bump an old thread but I am having the exact same issues with my car right now

I just swapped out my old oil pressure sending unit for a new one and I am having the same problems.......I can't really tell if the car has no pressure at idle by the sound because the thing is so damn loud at all rpms[8D]

Anyone have any advice? I don't really care to install a set of gauges in this thing, is there a way to tell the actuall pressure without installing a new gauge?

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1994 Mustang GT
www.cardomain.com/id/bigshirtlesspete

67mustang302

Get a gauge designed to read hydraulic pressure, just a simple mechanical, and d/c the sender and screw the gauge/line into the engine, you can at least see what it is at idle, and with someone helping you can check pressure vs rpm.

__________________
Who cares how much horsepower it has, all that matters is how fast it goes!

Best run 13.23 at 106.97mph with a 2.183 60'
Times from before tune and driver mod.

drhoward

I don't think I would be able to fit a pressure guage in there, its awfully tight

Is there any other way?

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1994 Mustang GT
www.cardomain.com/id/bigshirtlesspete