When cold startup everything is fine, after approx. 15 min. of driving the oil pressure indication will drop when I apply brakes to stop and the engine will then idle rough . I then place the truck in neutral and the pressure goes back up to normal. After 15 more minutes of driving it will not matter that I put it in neutral, but I have to idle the truck higher to keep pressure up. This motor has approx. 15,000 miles on it, the original motor was replaced a year ago.
Any suggestions at what to look at,check or replace before taking it to a shop.


Steve

 

What is the make, model, and, year of your application? Without such info, we can not help at all.

Are you getting any CEL codes?

What was the reason for engine replacement to begin with?

 

It is a 1988 Ford F150 XLT EFI 5.0 V8. No codes. The first engine had sat for awhile and ended up with to many problems that I decided to R2 it.

 

If you are going by the dash gauge, don't. Get a mechanical gauge on it or you're guessing at best. I chased an issue like this with a 74 FE and the oil pressure would drop as did the idle...which it's suppose to do. Turned out I had a crack in the intake manifold between the heat for the carb and the intake runner. As I always said, I wished I could find a girlfriend like that- blow and suck at the same time. I doubt the oil pressure is the issue but an idle issue. I'd be looking at the EGR and other sources of excess air.

 

if the engine knocks then its an oil pressure issue. but i would do as labnerd said and use a mechanical gauge.