My Granfather has a 97 dakota, in great shape, with the 3.9. Recently though, when you come to a stop, the oil pressure gets very low. He had a shop try to increase it mechanically with the linkage, but the computer just lowers it back down. We've been told we need a new computer. Is that true, or is there something else we can do?

 

Huh? It sounds to me like the oil pump might be worn out, or getting there. IIRC the computer doesn't control the oil pump, but I could be wrong. What linkage did you replace?

 

I don't think they replaced the linkage, I think they tried adjusting it. Yah, I know the oil pump has it's own control, most likely a spring mechinism like many others. It's the shop saying it needs a computer, and of course a new one is really expensive. We were hoping there was another way to increase the idle after it warms up.

 

Tell your grandpa to find a reputable shop. This one is trying to blow smoke up his butt! Oil pressure is controlled by the oil pump. If it is a high mileage truck it IS possible that the oil pump could need replacing although at idle as little as 10- 15 psi oil pressure should not result in damage to the engine. A good shop would check the actual pressure at a warm idle and go from there. My guess is it's just a high mileage Dakota and the engine is just showing it's age. At most it's probably just wear in the oil pump but an actual reading with a gauge should be taken to ensure the pressure is not too low. The computer and linkage bit is complete nonsense and he should NEVER return to that shop.

 

Thanks deranged, that's what I suspected as well. My ram frequently drops to 10-12psi at idle when hot, but jumps back to 40-60psi when off-idle. Cold start it's at 80 every time.

 

what is the oil level when it does this? If your oil level is low then look down into the intake and see if it looks like oil in the bottom of it. If there is oil down inside, your intake bed pan gasket is blown out. Very easy fix. Could be oil pump but would do it more than just on stops I would think.

 

The 3.9 is basically the old 318 with 2 cylinders lopped off isn't it? The old LA engines were notorious for low oil pressure at hot idle. I recall a 1970 shop manual (I think I may still have it) saying a minimum of 7 psi was acceptable! Man that's just kinda scary to me!

 

I know the throttle linkage has nothing to do with the oil pressure, well directly at least. Once it warms up the idle drops very low, and the oil pressure along with it. Since the oil presure is good throughout the rest of the RPM range, we're pretty sure its in good shape and doing what it's supposed to do. What we're trying to figure out is how to increase the idle, slightly, after it warms up, so that pressure won't drop so low. It should idle at least around 8-900 rpms. It now drops to around 500 after its warm. Is there another way to adjust the idle after it's warm?

 

I believe the idle is supposed to be 750 rpm's. On my son's '96 Dakota I did take the plug out of the throttle stop and bumped the idle up a bit. It idled irratic at first and after awhile settled down after it had "learned' the new setting. The throttle stop is on the left hand side of the throttlebody towards the front when facing the truck. His had a metal plug covering the screw that is there to keep you from tampering with it. You will have to "convince" the plug to come out to access the screw. It is VERY sensitve so don't turn it much! Maybe 1/32 of a turn is all it should need. While I am at it I should explain that the reason I adjusted his was because it would not stay running at warm idle and everything else checked out. If I were you I would FIRST check the ACTUAL oil pressure at hot idle and be sure that the pressure IS too low BEFORE attempting to do this adjustment.

 

Thanks for the help. Is there another way to get the computer to increase the idle after warm up?(my only scan tool is for late model VWs, I don't have anything for a domestic) It seems to be what lowers the RPMs so much, or at least the shop said so... Other than that it seems to be fine. We just didn't want to spend the $$$ on a new computer only to find out all it needed was a screw turned 1/32...