High oil pressure on gauge after change to synthetic?

[atblue5spzx3]

I have a 95 Explorer with a 4.0 of course, about 165k on it. VERY good shape, got it over the summer.


About 1000 miles ago, I went to synthetic, did the change and filter myself. No problems. Then, this week, I've noticed the oil pressure gauge is reading slightly higher than normal, usually the needle is in the back of the oil can emblem, left of center. Then the past couple of days, it's at times gone up to 80% of the range, and particularly at low RPMs, like when I'm cruising at 45 in 4th (5 sp manual). As an experiment, I went from a low RPM and gave it a bunch of gas and brought the RPMs to just over 3k and the needle almost literally fell as the revs rose until it was midrange again. I'm thinking gauge or sending unit, but I've never seen this kind of problem with a vehicle I've owned.

I have been checking the oil and in 1000 miles, the quality and capacity hasn't changed at all, perfectly full. It doesn't leak, smell, or have an exhaust change.

The check engine light is "EGR flow insufficient".

 

[Maniak]

You can relax somewhat, they aren't related...

The oil pressure gauge/sending unit combo is actually an analog idiot light. It doesn't move based on oil pressure. It is using a ballast resistor to "try to" keep the needle in the center.

There are a few good theads here about the analog idiot light (fake oil pressure gauge).

As for the Cel, My first guess would be plugged egr tube, then dpfe sensor but those with more 2nd gen experience (with EGR) should chime in.

~Mark

EDIT: I found one of the threads I was thinking of. http://www.explorerforum.com/forums/showthread.php?s=&threadid=14894

 

[atblue5spzx3]

That makes a lot of sense........twice I've seen it twitch significantly, going from 60% to like 90% and back.

The CEL doesn't concern me terribly.........my Focus has had the CEL for both DPFE and EGR, no worries. Doesn't affect drivability at all. Anything that could concern oil pressure gives me pause heh....especially since I have a 300 mile journey tomorrow.

 

[SoNic67]

Check your voltage with engine running. Looks like it is low on the gauge - if measured is some 13V, you have a bad alternator. That might throw some weird codes and explain some of the stuff is happening too...
If it is 14.4V you are good.

 

[atblue5spzx3]

Check your voltage with engine running. Looks like it is low on the gauge - if measured is some 13V, you have a bad alternator. That might throw some weird codes and explain some of the stuff is happening too...
If it is 14.4V you are good.

It's a brand new 130 amp alternator.......without gas it does dip, but with gas runs fine....as far as I can tell it's got to be the volt regulator....battery was tested and is fine. Thanks for the input though, it's appreciated.

 

[atblue5spzx3]

You can relax somewhat, they aren't related...

The oil pressure gauge/sending unit combo is actually an analog idiot light. It doesn't move based on oil pressure. It is using a ballast resistor to "try to" keep the needle in the center.

There are a few good theads here about the analog idiot light (fake oil pressure gauge).

As for the Cel, My first guess would be plugged egr tube, then dpfe sensor but those with more 2nd gen experience (with EGR) should chime in.

~Mark

EDIT: I found one of the threads I was thinking of. http://www.explorerforum.com/forums/showthread.php?s=&threadid=14894

Sweet thanks for digging that up, when I did a search I didn't find what I was looking for nor that thread.

Weird that poster has nearly the exact same issue, except his needle went the OTHER way at the same mileage post synthetic switch. Very weird.

 

[rhauf]

my '93 has the same type of oil pressure gauge (analog idiot light) and it used to read about half scale, then it started reading lower, about quarter scale.. now it reads 3 quarters scale.. i've been running synthetic the whole time.

i'm sure the oil pressure in the engine hasn't changed, it's just the stupid gauge.. it doesn't read anything worth noting (except that there *is* oil pressure at all)