low/dipping idle, low oil pressure
 

The car was behaving great until just yesterday. The drive to work was fine but, when I got in my car to leave, It didn't rev up like it normally does. It went straight to about 600rpms. On the drive home, I noticed that coming to a stop, the rpms would dip back down to this point before hitting 850 again. Never felt like she wanted to shut off though. When I got home, I spent some time looking for loose connections and vacuum leaks but came up empty by the time it got dark.

Today, I went out to start her and noticed the oil pressure was low, like 10psi at idle. The oil only has about 700 miles on it. Still looks good on the dipstick and isn't low.

When I went back out a little bit later to shoot this video of startup, oil pressure was... well, check the link below. any ideas? I searched but couldn't come up with anything that matched these particular symptoms.

thanks in advance.

Oh, forgot to add. Car is 1995 R2 with sequential twins running stock boost pattern. About 6000 miles on rebuilt motor. Mods include full exhaust, hallman boost controllers, intakes, SMIC, and PFC.

edit: I have also noticed the 3000rpm warmup hasnt been happening since this started either.

I think this may be your oil pressure indication prob.

no idea about the rpm's

| Repair Guides | Sending Units And Sensors | Oil Pressure Sending Unit | AutoZone.com

The sending unit was the most common thing I came across, searching about low oil pressure. I was just hoping there was something that might have caused both these issues to arise simultaneously. I was thinking that the sending unit wouldn't affect the rpm but low rpms might affect oil pressure, maybe?

anyway, i'll probably go out today and have a look at the sending unit, maybe send off for a new one and see if that fixes the oil pressure reading at least.

Low RPM will affect indicated oil pressure.
Sending units go bad but frequently it's just a matter of a bad connection. Before you buy a new sender
clean the spade connector at the sensor. It gets dirty because it's right underneath the oil filter pedestal. And I think the weak signal during low idle can't get through. If I recall correctly from the FSM you should see about 55 psi at 3000 RPM but check for yourself to make sure.
For the dipping idle I would check to factory service manual troubleshooting. Offhand my first thought would be the idle air control (IAC). It will carbon up overtime. Easy to remove and a little brake parts cleaner will usually clean it up pretty well.

Thanks. I'll give that a shot and post the results.

I second that. You should be reading about 10-20 psi on idle and 600 RPM is a little bit low, but that is an easy adjustment. The car is probably just getting back to being driven daily from whoever you bought it from. There is a lot of good information about TPS adjustment and throttle adjustment in the forums. The stock gauge on these cars are garbage.

I've been driving her near daily for about five months until this happened. On the bright side though, I went through, cleaned the connector on the sending unit and the IAC. Noticed the connection on the AWS was loose and pushed those back together. Rechecked my vacuum hoses, ect. And changed the oil for some piece of mind.

Now, oil pressure is good and she's driving great. Thanks everyone.

I disagree. I don't think they're junk and my sender is original to my car...now 23+ years old with ~ 120k on it. Occasionally I'll check the connector to make sure it's snug and clean with a spritz of electrical contact cleaner, but that's it. While others are spending money buying unneeded OEM senders or boy-racing out their interiors with unneeded aftermarket gauges, mine's doing just fine....just like the OP's.

I was more referring to the gauge itself. As long as the sender is cleaned regularly, it should last quite some time. But the gauges over time become more and more uncertain. If calibrating test equipment for a living has taught me anything, its that you should never really trust a gauge that old.

I don't understand. Resolution on the FD gauge isn't very precise, but IMO it doesn't have to be in most cases. Given all the variables involved with oil pressure...viscosity rating, ambient temperature, engine temp, fuel dilution, rpm, etc, it's really a relative reading that you look for in a street car. Most owners know what's 'normal' for their car under the given circumstance and know at a glance if there's a problem. Given that, calibration is like shining tennis shoes. Besides, seems like the average car doesn't even offer a gauge anymore, just an idiot light. And if they do have a gauge, resolution is similar to the FD's.

I calibrate test equipment day after day. I guess I'm just picky and want to know the exact pressure, not just an approximate. Once upon a time, these gauges were probably dead on, but time takes a toll on stuff like that.