oil pressure drop/car stalls

[elderstang]

My daughters mustang runs great and holds good oil pressure for 15 to 20 min. then if its at 1000 rpm or less the oil pressure drops to zero and the car stalls out. If you start it back up and keep it at 1500 rpm and up, it holds great oil pressure again. until you let it idle again. Does the oil sending unit and the computer shut the car off when the oil pressure drops like that? The motor only has 20k on it since a rebuild. Its a 95 gt w/ an automatic. Thanks for any help.

 

[Chythar]

The oil pressure gauge is mostly a dummy gauge on our cars. Once the gauge reaches a certain point, it doesn't go up or down much if at all. Once pressure drops below a certain point, the gauge drops.

Since the oil pump is run directly off of the distributor, a correct oil pressure gauge would show rising pressure as the RPM's went up. This worries the average consumer, so Ford put in what amounts to a dummy gauge.

I think you're running into the reverse problem - your daughter's Mustang isn't idling properly. When the engine dies, the gauge drops to 0. I'd recommend resetting the idle using these instructions.

The IAC motor could also be bad. It's the big black sensor on the side of the throttle body; it lets the engine idle when there's a drain on the motor at idle, such as running the A/C. Reset the idle first, then you can test the IAC.

 

[HISSIN50]

Chythar is right-on (the sensor's drop-to-zero threshold is 6 PSI).

The first thing I would do is to hook up a mechanical OP gauge. Even if you dont want to permanently have one installed, toss it on and watch it to ensure you have adequate pressure at all times. You can remove it after you've confirmed this (hooking up one in the engine bay for a minute can take but a few mins, depending how much you fight removing the stock sender).

Unlike some GM's, the fuel pump circuit is not tied into the oil pressure circuit.

I also agree that there well could be an idle or other issue with the car. Pull the codes just to be sure nothing is stored in the EEC (codes can store without illuminating the CEL).

Good luck.

 

[elderstang]

I put a new sending unit on this morning. i also changed the oil, just in case. It did the same thing. I can start it up cold and it runs great and holds great oil pressure. i drive it 3 miles and it does the samething. today the oil pressure dropped to 0 @ 2000 rpm. I dont get it. I had this motor in my vert and it always ran great.

 

[HISSIN50]

Again, put a mech gauge on there so you can see what's going on. There's NO other way to know.

 

[revhead347]

I would agree with everyone else here. It's not an oil pressure issue, it's an idle issue. Most likely it's the IAC. They are notorious for going bad in our cars.

Kurt

 

[Zero_chance]

Now, is the car stalling and then the oil pressure drops, or is it dropping while running and then shortly after the car stalls? Does it run really rough after the oil pressure drops? Noises from the engine? Just thinking out loud here.

 

[HISSIN50]

today the oil pressure dropped to 0 @ 2000 rpm.

Quoted just because I'm not sure people saw this.