Opinions on oil pressure

[masoQist]

I recently installed an oil pressure gauge in my 1990 Q. Someone previously posted that they could change out a sender in a few minutes. Indeed, to my surprise, it can be done in 5-10 minutes!

Anyway, the history of this engine is basically unknown. I'm running Shell Rotella T6 5W-40 synthetic oil. Ambient temperature was about 70F, and readings were taken just after a highway drive.

11 psi @ 600 rpm
13 psi @ 700 rpm
41 psi @ 1500 rpm
71 psi @ 3000 rpm

The 3000 rpm reading is within the FSM spec., but the idle reading is a little low (should be 14 psi minimum). The FSM seems to suggest to look for problems if "differences are extreme". Should I be concerned about the condition of the lubrication system? I'm guessing not.

[Q45tech]

Was this with a brand new oil and oem filter [absolute worse case]. PSI goes up as oil gets more miles due to viscosity increases.
I wouldn't be too worried AS BRAND NEW BEARINGS might only add 2 psi.

Obviously you should reset hot idle to 675 rpm minimum.

[masoQist]

I'm away from the car at the moment, but I beleive the oil has a bit less than 400 miles on it. The filter is non-OEM. IIRC, it's an AC Delco, which is probably a Champion Labs filter [I know this is supposedly a crap filter - I'll get a better one next time ]

The IAC valve is unplugged at the moment because it is forcing the idle too high. When connected, it raises the idle to 760 rpm, which is completely unacceptable. I'll be doing further investigation into that problem soon....

EDIT
Note – the information regarding idle speed in this thread is misleading, and is an excellent example of why you need to have the factory service manual that is specifically for your year of car. For my 1990 q, the idle is supposed to be set at 670 with the iacv disconnected. Then, when the iacv is reconnected, the ecu is supposed to boost the idle to 750 rpm. When i first posted this, i was using the free online manual for the 1994 model. Idle specs are very different from a 1990.

[Q45tech]

OEM idle spec is 670 +- 25 rpm so 645 rpm at 176F coolant is minimum, but 695 rpm is probably a better choice in summer with AC on.

As the engine ages and compression declines it is alway assumed that technican will boost rpm to smooth idle under worse case parasitic loads.

Much depends on wether you meet the maximum of 14 psi compression between cylinders or 25 rpm range during a power balance.

[masoQist]

Thanks for the info. My ECUTalk cable recently arrived, and I'm really looking forward to doing a power balance!