Oil pressure at idle

[tcowles]

2008 4.0 sohc with 134,000 miles. I had all the chain tensioners replaced and the oil light is on from idle to about 1700 rpm. Truck runs good with very little engine noise. Before the chain tensioner failure the motor ran great and did not have the oil light problem.
The mechanic checked with gauge and has less than 1Lb at idle and goes to 5 lbs at 1700 rpm.
Mechanic tried these items to fix the oil pressure.
1. Used an engine flush and replaced oil with new Motorcraft filter and 5w30 oil.
2. Replaced the oil pump and said the screen was clean.

I drained a quart and added Lucas oil stabilizer with no change to the problem.
Today I confirmed the oil pressure with a gauge - no change from what the mechanic found. Reving the engine did make the pressure rise but never went above 10 lbs.
I decided to drive the truck for a week and see if anything changed. I have put about 400 miles on it without additional symptom.
From my research, 2 items might be the problem.
1. Oil pump screen is cracked and sucking air thus lowering pressure.
2. Main timing chain guide is loose and allowing oil to dump into the front of the engine before getting to the pressure switch.
Looking for other things my mechanic can check.

 

[DILLARD000]

OilPumpScreen is inspectable\cleanable\replaceable
by dropping OilPan; one bolt to remove it from OilPumpSuctionTube.
It is plastic & has an ORing seal\seat, so its possible that when OilPump got changed, that SuctionTube &\Or Screen got cracked or that ORing cracked & did not get replaced. Or that this Screen got left off, or new OilPump may be bad; new part does not always mean its a good part.
When I last did PanDrop, installed SpringClamp around Screen~To~Pump connection to help keep it tight.

 

[tcowles]

Thanks Dillard,
I will give your photos to my mechanic today.
I hope he can find the problem. I love the truck.
‘TJ