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Oil pressure

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I decided to go for a cruise in the Reatta today. Started the normal way as of late (Fires up then loses RPM until it slowly just dies unless you tap the gas). Everything looked fine until it got up to operating temperature, then I noticed while I was idling my oil pressure would drop to 22 PSI and then go up to 30, then to 24 etc. As soon as you give it gas it will increase to the usual 40-60 PSI from 1200-2200 RPM. But as for the idle pressure, alot lower than usual. Ive never seen it drop below 30 before. Usually I idle between 32-35 PSI.

The only thing I have changed recent is the ignition, wires, and plugs. (Switched to Delco unit, MAN can you tell the difference at low RPM!)

I also cleaned out the EGR Valve and put new gaskets in as I noticed some smoke coming from it when I cleaned my injectors.

That was a week ago and even after doing the Delco upgrade it hasnt dropped oil pressure until today...

Not to sure where to go from here. Im taking it in tomorrow because of the 100rpm surges at idle and for a couple other things. Should I just get them to check or could I run some easy tests myself to cancel out some problems?

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if i recall correctly, the oil pressure sensor "takes over" from the fuel pump relay after starting. mine was bad, finally showing 0 to 255 psi pressure on the CRT. perhaps yours is going out. that's where i would start - might be that's where both of the issues are coming from - if not the IAC for the idle.

also a compression check on the cylinders. the rear 3 are a PITA to get to, but if any of the front 3 show a vast difference of compression, then it would be time to investigate the internals before you go back there:)...

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Thanks, ill put a new oil pressure sensor in and do a compression test and see how that goes after I get it back.

ill try to do it before I take it in but I doubt I can find a new sensor in this hell hole.

thanks guise

ps I've cleaned the iac and MAF sensor with no results

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since i've heard you can't get "The Reatta Store" parts via Amazon in the "Great White North" - i don't know why - i can get Tuborgs here:p, here's a couple links:

Buy BWD Engine Oil Pressure Switch S4151 at Advance Auto Parts

Duralast/Oil Pressure Switch (PS298) | 1989 Buick Reatta 6 Cylinders C 3.8L FI OHV | AutoZone.com

they are "special order" here, so it would take at least overnight to get them to my store... maybe a NAPA type flaps, or a GM dealer may have them in stock up there...

hope this helps!:)

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Way ahead of you, I already picked it up! :) came to 67$ cad so approx 60$ us

Edit: a few places carried them but not in stock. Managed to grab on to one from a small flaps store here.

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Also yeah price difference is a lot, but winter is coming fast and Canadian shipping likes to take its sweet time.

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Would one of you lovely gents send me in the right direction to install this thing. I have no idea what I'm doing and can't find much online for the series 1

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Brendan,

Oil Pressure sender location.

Pic #1.) post-67519-143142056708_thumb.png

Pic #2.) post-67519-14314205672_thumb.png

In pic #1) Just left of the water pump housing and below the power steering pump.

It's the silver tube like thingy with a hex base and black plastic top.

In pic #2) Looking down, leaning over the right side fender, the black plastic top of the oil pressure sender, with the four pin connector, can be seen just to the right of the R.H. CV joint.

John F.

post-67519-143142041147_thumb.jpg

post-67519-143142041151_thumb.jpg

Edited by Machiner 55
Added annotation to pics #1 & #2. (see edit history)

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Is there a special took I need or do I just loosen (what looks to be some kind of) a nut at the base? I thought I read in a forum that it needed a special tool, is this true?

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No special tools needed. Remove the electrical connection. Don't try to twist on the back part. Put a wrench on the metal hex to loosen. I have changed with a pair of channel locks when correct wrench wasn't handy.

post-52331-143142041234_thumb.jpg

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No special tools needed. Remove the electrical connection. Don't try to twist on the back part. Put a wrench on the metal hex to loosen. I have changed with a pair of channel locks when correct wrench wasn't handy.

<img src="http://forums.aaca.org/attachment.php?attachmentid=204755"/>

I used channel locks on the last one I did. The new one had a bigger hex head than the old one as well.

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Just a note. The threas on teh sensor are tapered pipe threads. No o-ring or seal is needed. Tighten down good and it shouldn't leak. Go back an tighten a little m ore if it does. Over tightening can deform the pipe threads and make them more prone to leaking.

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Changed the sensor, now it shows 46psi no matter what I do.. is the sensor faulty? It only goes up to 47 when I drive past 2000rpm

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Brenden,

What does it read at idle? Is there fluctuation in pressure or does the pressure hold steady at a given, set RPM?

John F.

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It reads 43 psi at idle now after taking it for a drive. I noticed it move a bit more. With engine off its at 0.

edit: seems to only fluctuate 5 psi

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Sounds like it is operating normally, if the sensor stuck at a set reading it wouldn't zero at engine off.

KDirk

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Ok good thanks. What does closed and open loop mean? I got an electrical warning screen but no code. I go into service mode and it shows its in open loop (which I've never seen) and the oxygen sensor doesn't move from .81.. this can't be normal

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Here's the oil pressure on my '86 3.8 Park Ave. It is best to use the gauge. The new engine came with the wrong timing chain cover gasket and partially blocked the oil port. It was only running about 8 PSIG upon installation- good thing we checked with the gauge.

We had to find the correct gasket and R&R in place.

034mna%20%282%29.jpg

Bernie

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Brendan, your oil pressure reading(s) also seems to me to be ok.. mine runs a little higher (50+) when cold, then around 47 warm at speed. upper 30's after that at a "hot" idle.

regarding open & closed loop, i'll the the "puter experts" explain. all i recall is reading something that it changes at around 140F.

i "googled" "open loop vs. closed loop" - this is the first thing that popped up: Definition of Closed Loop vs Open Loop

since the link is about furds, the figures could be totally off - or the whole thing...:P

have you replaced your O2 sensor?

EDIT: agree w/60FlatTop on using a "non-electronic";) gauge before going further if the problem resurfaces...

Edited by Corvanti (see edit history)

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That definitely helps, thanks.

Yes the 02 sensor was replaced a couple weeks ago.

Now that I know about closed and open loops I understand why the oxygen sensor was at that same reading. :)

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Basically the engine runs in open loop when cold. The ignition and fuel are set via lookup tables in the computer. Once the engine has warmed up a bit, the O2 sensor in particular, the computer can use the various sensors to fine tune the ignition and fuel for {power, mpg, min emissions} - depending on situation. It is the reason O2 sensors are now 'heated' at startup. Helps get things into closed loop sooner. (California-bound cars got heated sensors a couple of years before the other 49 states. Of course heated O2 sensors cost about 2x what non-heated sensors cost...)

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As I recall going from open to closed loop is on a timer: 125 seconds from cold start and 25 seconds from hot. This gives time for the O2 sensor to fire and is a function of EGT and not coolant temp.. The computer also does a few things at a coolant temp of 146F like TCC enable and is "all in" at 158F. I run mine with a 180F thermostat and reprogrammed fans to keep coolant temp under 190F. Everything under the hood lasts longer.

I have noticed that the "C" engine in the Reatta always seems above the factory spec of 40 psi at 1875 rpm and usually see above 40 at hot idle.

The FSM recommends using a mechanical gauge if in doubt, the oil pressure senders are notorious for going bad and giving false readings.

Edited by padgett (see edit history)

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Got it all figured out, thanks! She holds steady at 40-44 PSI at idle now and 46+ at 1800 RPM

I still think my engine runs rich though, is this all electronically controlled on these cars or is there a way to tinker with it manually?

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