I've spent a lot of time searching for the fix to this and haven't found a solid answer. 2003 Ranger 3.0, 4x2 with 145,000 miles on it. Idle at low engine temp, the oil pressure gauge is fine, right in the middle. After engine gets to temp and driving, pull to a stop and at idle the pressure gauge flickers back and forth. Once a load is put back on the engine it goes away. I am aware that this is a dummy gauge and when the PSI drops below 8psi it gives a low reading.

Truck runs fine, does not leak any oil, does not burn any oil and no audible knocking from the engine.

What I've done so far -

- New Cam Position Sensor @ 140,000 miles
- Replaced Oil Pressure Sensor
- Using heavier weight oil - 10w-40

What I've seen as possible fixes:

- Checking the electrical grounds on the sensor. (don't think this is the issue but possible)
- Install a oil cooler on the truck, someone on YouTube fixed the problem this way. Said the oil gets thinner as it gets hotter and sends a low pressure signal. Makes sense but expensive and time consuming to install.
- Possible cam bearings worn
-Possible low idle/stall indication sending a false signal

Looking for any help with this or a definitive answer to get this corrected. Some say to just ignore it but I'd like to exhaust all solutions to prevent any major engine damage.

 

Around 1988 Ford switched over to Oil Pressure switches, on/off, open/closed, its a switch, 5.5psi is about the cut off for on/off, 5psi off, 6psi on, but its not super accurate, as long as pressure is above 4psi all will be well with the engine, you WILL hear valve train "ticking" noise if it drops below 4psi

The switch just has 1 wire, this wire is the Ground for the oil gauge on the dash, when grounded gauge shows in "normal" range, where in normal range depends on voltage, so gauge can go up with RPMs, but that not pressure changing, that's the alternator putting out higher voltage, just FYI

Because the switch only has 1 wire, that means the THREADS on the switch are the GROUND it needs, so NO TAPE on these threads, need BARE threads for a good ground to engine

You can unplug the 1 wire connector and then Ground that wire, so key on engine off it will show normal pressure
Start engine and drive it that way and see if gauge still does its "bouncing thing"
If it does then its a wiring issue
If it doesn't then its a switch or pressure issue

If switch or pressure issue then remove switch
Disconnect coil packs 4 wire connector so No Start
Put rag/towel around switches hole
Crank engine
This will push any debris in that passage out
Clean up the mess, lol
Put switch back in with BARE threads
Plug connector back in
Drive and see if its better now

 

Thank you for the suggestions. I did not think of the threads being the ground. I don't think I taped the new switch when I put it in but I'm so used to taping threads to seal them I may have. I will try these and see if it helps.
Really appreciate the help!

 

General rule of thumb for WARM oil pressure is 10psi per 1,000rpms
So engine idling at 800rpm should have 8psi
Running down the road at 3,500rpm expected pressure would be 35psi

If your idle is dropping down under 650rpm, 6.5psi, then you could start to get gauge flicker

 

Tried what you suggested last night. Switch is grounded correctly. Tried the clean out method (with minimal mess), Still flickering after driving at temperature.

Truck is idling at around 800rpm (according to the gauge) when the flickering is occurring.

Any other thoughts? Or should I just ignore it.

 

If you are not hearing valve train noise then oil pressure is not low enough to worry about

Is the New oil switch Motorcraft brand?
Thinking 3rd party might be opening at 8psi so flicker at 800RPMs

 

That will be the next thing I re-check. When I originally put the new oil switch in 6 moths ago I got it at Autozone and I think it was a Motorcraft part but it may have been an aftermarket Duralast.

The quest continues.

Again, thanks for the help.

 

Just to update you. Pulled the existing oil pressure sensor out. It was a Duralast. Ordered and installed a new Motorcraft sensor. Problem solved and lesson learned.

Again, appreciate the help.

 

Good work

Thanks for the update and THE FIX

 

Had the same problem myself last year. Put a Duralast sensor in, it failed two months later. Motorcraft switch went in, and has been fine ever since. Since my truck has high mileage, I also opted to install an aftermarket oil pressure gauge, just so I can monitor the actual oil pressure.

 

I had this exact same issue and it ended up being my alternator going bad. It was reading fine at the time that my gauge was bouncing around so I didn’t think anything of the alternator. But a month later the alternator went out all the sudden and after I changed it the issue went away. Turns out with research the systems were tied together. Who knew lol!

 

I know this is an old thread. But the same thing happened to me. Ended up being a vacuum leak. In case somebody else gets stumped and can’t figure it out