I just bought a 97 F-150 with a 4.2 V-6 with 110,000 miles. It runs excellent but after it warms up, when I stop at a light, the oil pressure gauge drops to low. I put it in neutral and it goes back up. As soon as I give it some gas, it goes bask to normal as long as I'm driving. It runs smooth, has power, I just happened to look at the oil gauge today and it was going up and down. Has anyone had this problem? I suspect a clog somewhere or a bad oil pump. Maybe the oil pick up tube but how can I check that? Any help would be appreciated, thanks in advance/ Billy

 

Low as in the gauge is as low as it gets, and the light comes on or is it the type of low where its under what it normally is?

 

You might just need a new oil pressure switch... the gauge on the cluster is really an on-off type of deal... almost like a dummy light. It doesn't indicate pressure or oil level. IIRC, if working correctly, if the oil pressure drops below 8 psi, it will send the needle to L, and will illuminate the red oil light.

 

Ya my 2000 5.4 does the funky on off flash, damned dummy switch is all gummed up. spring and ball in the switch wear out from stop and go driving from what I have dealt with before. Sensor up here is worth a measly 50bucks or so

 

The gauge goes all the way down, no light though. As soon as I put it in neutral or take off, it goes back to normal

 

I'd say replace the oil pressure switch... it's by the oil filter...

 

X2
I replaced that in the expedition when it did the same thing, and it worked fine after that.
Sending units in them werent all that great if I recall. Especially in super cold.

 

It doesn't have a Fram filter does it?

I've also seen simular if the oil is over filled-it can get air bubbles from being whipped up.

Just a thought, probably is the switch tho.

 

Thanks for all the help, a $7.00 switch fixed the problem. Thanks again, Billy

 

Good to hear you got it fixed.