Oil pressure problem... this is driving me fword nuts

[kings-x59]

In a nutshell, after driving for about an hour, maybe a bit longer my oil pressure drops by half.
After the drop in pressure, the engine has less torque and dogs a lot.
AND I am freeking stumped ](*,)
When the engine first hits operating temperature and for a while after that, the oil pressure is great.
It's been doing this since I got the van in '04. I change my oil every 3K. (I"m not the original owner of the van so I don't know the whole history on it's maintenance).
The weight of the oil has no real effect. 10W30, 20W50 makes no difference. With a new oil filter, I see higher pressures at the top and bottom of its operating scale, but I still see a 50% pressure drop after driving for an hour or more.

The engine has 113k miles on it. I've replaced the oil pressure sensor with no improvement. On start up, the oil pressure gage tends to hop around a bit. It has a small leak at the drivers side lifter cover and a small leak at the rear main seal. But, these are so minor that I don't have to add oil between oil changes. The engine isn't burning oil. There's no oil in the cooling system. The engine is not running hot. I am...so.... confused

I've tracked the wire off the sensor as far back as I can without splitting open the harness, and put some wire loom over it in case it was grounding where exposed.
The oil pressure came up in general a substantial amount after I rebuilt the throttle body and cleaned the carbon out of the totally blocked pcv port. So blow by gas pressure in the crankcase is no longer a problem.

It appears to be temperature related, but wtf is it!!!??? please pardon my frustration. I have this serious astrocrak thing.

I need some help here.
Anyone experienced this, or have any suggestions. My patience with the "pig" is growing short.

P.S. I am a stubborn sob from line of depression era deep east Texas dirt farmers and I don't like to throw away anything I can fix. So please, no one suggest a V8. I'll do that after I can't get another mile out of this 4.3.

[uncle-vinny]

Sorry for asking a dumb question but what does "it dogs a lot" mean?

[astrozam]

What temp t-stat are you running? does your rad have both the oil cooler resevoir and tranny fluid resevoir on the sides?
Have you checked your Tranny fluid level lately, both cold and hot? do you run an aux tranny cooler?
Have you checked for any codes?
Are you running a cat? if so, new, old, Hi flow?

[kings-x59]

loses power when you hit the gas, must be a Texas saying. As in pants, runs slow like a hot tired dog.

[kings-x59]

I"m running a 195* t-stat. I have only the trans cooler in the radiator, no oil cooler. I'm running an B&M trans cooler 2" in front of the core. No codes and tranny fluid level was good hot when I changed the engine oil week before last. I haven't checked it cold.

This is making me crazy. I keep thinking, well maybe the oil return ports are partially sludged up and the lifter covers are slowly filling up with oil and the pick up screen is starving for oil...but I'd expect the gage to bounce around at this point which it does not, just drops and stays steady at half mast. ](*,) ](*,) ](*,)
When the oil pressure is up, the van runs really good for an old gal. when it drops it absolutely geriatric.

[kings-x59]

One last symptom: the idle RPM drops quite a bit and flutters sometimes when this happens.

[peter]

I don't think the two are directly related.

Oil pressure; What numbers you talking about before & after the magic hour? My 502 easily runs half the normal start-up oil pressure at idle once the engine's warmed up. As well, you mentioned that the idle drops quite a bit once warmed up. If the engine's "fluttering" or idling at a lower than normal rpm, oil pressure will drop as well. Even more so in a 116K engine.

On the highway with an already warmed-up engine, my oil pressure drops by at least 15% after awhile.

I think you should start off by connecting a known-to-be-accurate mechanical oil pressure gauge to her and look to see what actual pressures you're running. And don't foget, you ain't got no spring-chicken there. 116k miles is, after all, 116k miles. She's earned the right to a few squeaks, groans and lower oil pressures. It ain't as easy to "get it up" when you're older, you know

Your engine perf. issues are, I am almost 100% sure, not related to your oil pressure.

[ScottS]

I would suspect the relief valve n the oil pump - maybe as the oil heats up the spring gets warmer and relieves at a lower pressure- It would be worth it in my opinion to

1. Install a mechanical gauge to verify what is happing

2. Replace the oil pump and relief just to see if it improves

3. if your engine bearings are worn to the point where you are losing oil pressure a higher volume pump my delay the inevitable

[GEJ]

I would suspect the relief valve n the oil pump - maybe as the oil heats up the spring gets warmer and relieves at a lower pressure- It would be worth it in my opinion to

1. Install a mechanical gauge to verify what is happing

2. Replace the oil pump and relief just to see if it improves

3. if your engine bearings are worn to the point where you are losing oil pressure a higher volume pump my delay the inevitable

I agree with what Scotts said and would add that I was a 20+yrs user of Fram oil filters.Don't remember who it was,but someone posted a review of oil filters here and I changed to a Wex oil filter because what the review said about how bad the Fram oil filters where.I saw a raise in the oil pressure at all rpm ranges.The Wex filter alone did that.Not a fix,but something.Worn engines should give you 30 to 40psi while driving and no less than 10psi while at a idle.Some I have seen say 7psi at a idle,but I think that is dangerously close to a line of no return.

Oh yeah,I do agree with Scotts,but a high volume oil pump could make a poor oil drain back worse.Sucking more oil out of the pan and still not having it drain back.

Some here are big fans of a product called Seafoam which is added to the engine to clean it out.I am not one of those because I think there is a risk to clean out sludge that is taking up clearances on worn parts.You might want to give it a go if you think it will help.

[kings-x59]

Gary, I read that oil filter post too. Used to be a Fram user. I'm running mobile 1 filters now.
Peter, thanks for the reality check. I think maybe I'm making a mountain out of a molehill.
I priced a replacement oil pump - not expensive and replacement looks simple enough, just messy.
Scott's scenario sounds entirely plausible to me. I guess my first step is to get ahold of an oil pressure test gage and beyond that decouple my thought processes on the oil pressure and fluttering idle issues.
Thanks for the input guys. I'll post a follow up when I've got some positive progress to report.

[Rebel]

I don't think the two are directly related.

I agree with Peter. I also think you have another issue which is not related to oil circulation. The norm is, as you know, higher pressure when cold and drops as engine and oil warm up to running temp. Sounds as if all is good to this point but then after warming up you have an issue with no power or as you mentioned, the motor dogs out. A term used here in the south. Question is,,what's causing the power lose, power loss that reduces oil pressure caused by lower RPM range. My question would be, what's causing the power loss ?

[kings-x59]

Thanks Reb,
The input from everyone has helped my state of mind. For one, I may be expecting too much from an engine with this kind of mileage. I have tendency to baseline old engine performance on my 96 jeep engine w/ 180,000 miles on it. For two, I can think myself in circles pretty dang quick when I see multiple symptoms pop up.
I see that I need to break the symptoms down and address them individually. I drove the van for just under 2 hours around noon today, combination of surface street driving and freeway driving. Oil pressure did its usual thing, dropped by half after an hour or so. I misstated the case on the idle flutter in my previous post. This doesn't happen all the time - maybe half the time. It didn't happen today.
I think Scott may be on to something with his thoughts on the oil pump. An additional thought I've had for sometime is to add an engine oil cooler. I drive some really grinding rush hour traffic 5 days a week.(put a cooler on the trans a long time ago). I've even toyed with the idea of venting the hood ( scoop, louvers... something) to disipate the heat out of the engine compartment.
I think I need an astrocrak intervention. I can think up things to do far faster than I can implement them.

[SoCalli V8]

First you have to install a mechanical gauge to verify what is actually happening within your engine, then go from there.

Post the results.

[kings-x59]

cold use some pointers on doing that. never done it before. does it screw in to the oil pressure port or what?
btw, when you going to put some formal wear on that slut? your primer looks better than my oem paint. mine looks like a case of leprosy.

[SoCalli V8]

cold use some pointers on doing that. never done it before. does it screw in to the oil pressure port or what?
btw, when you going to put some formal wear on that slut? your primer looks better than my oem paint. mine looks like a case of leprosy.

Yes it will screw into the oil pressure port.

My slutty van jus` enjoys being driven around semi naked...... She is a Hooker, that takes most of my money......


And I don`t even get a Bj in return...... wosupwiththat?

But she sure looks Sexy, and always gives me a stirring in the front of my shorts......