NEED HELP Oil pressure

[MILES-2005-4.2]

My oil pressure is fine for until fully at operating temperature. I drive to work on the highway about 40 miles, then have a couple traffic signals before I get there. When I am on the highway my pressure is fine when I stop at light it falls. When I give it gas it goes back up.
My other is issue is a stutter /spit when at idle and when on an incline at highway speed.
I need this truck to stay reliable as I cannot afford to trade it in and I do love it. I had cluster rebuilt about a year ago and about two months ago I put a new throttle body and plugs in it. Helped for a short time.

 

[TollKeeper]

Well remember that the oil pressure guage on the 4.2 is a dummy gauge. It only tells you what the oil pressure it thinks it should be based upon RPM and it reading some sort of oil PSI, unless there is no oil pressure. The factory Oil Pressure switch works on a on or off principal, and the readout on the cluster is the computers best guess. So the 40 PSI, I would rule that as a ghost number, it has pressure, but how much is anyones guess. Check your oil pressure gauge, if not replacing it. Then check your idle oil PSI. If its still -0-, than you might have a much bigger issue going on.

The oil pressure switch is a common failure point if the plug is oil soaked. So unplug it, and look at the terminals. If they are oil soaked, than replacing the switch is needed.

 

[Mooseman]

And if you would like further explanation of the fake oil pressure gauge:
Trailblazer oil pressure gauge doesn't tell you the oil pressure (4.2L engines) (YouTube)

 

[Mooseman]

If replacing the switch does nothing, I would suggest that you stop driving it and do a proper oil pressure test. If you follow along with this guy's videos (7 total), he ultimately had to remove the pan and clean the pickup tube which was 90% clogged. His symptoms are exactly the same as yours.

Reason I say to stop driving it is because normal oil pressure on these trucks should be between 50 and 70 PSI on a real gauge (not the fake one on the dash) and I estimate he was just around the switch's cutoff, which is about 4 PSI. He's lucky he didn't do any damage.

 

[6stringbass]

How many miles do you have on the car? Higher mileage cars tend to have some other issues involving oil pressure (and I know first hand!).

 

[mark'stb]

I have a stand alone oil pressure gauge on mine. Hot idle it's around 7 psi. I went as far as putting on a mechanical gauge- same 7 psi. That was probably 8 years ago. Has 225,000 miles on the original unopened engine.