Oil pressure at idle '76 911 and other stuff..

[calling911]

I just started driving this bad boy last week.. never owned a P car before. the guages sometimes shake wildly which I will try and cure by cleaning up connectors.. BUT.. last night while driving home in traffic I noticed when the temp gauge read 210 my idle pressure was nearly 0. at 2000 rpm it was oh around 15 (my gauge seems to read PSI not BAR).. then a little while later, still with temp reading 210 (is this oil temp?) it read about 6-8psi at idle.. so I am not sure what is going on.. all my test equipment is in my moving truck so I can't latch on and test real pressure right now..

Anyway.. my question is, does the sender go bad very often? Should I just replace the darn thing at 180 k on the ODO? (I dont know if she was ever rebuilt)..


Also; why is my gauge in PSI? Is this unusual? This appears to be a california car..

Also; the advance vacum line is disconnected and plugged.. why? I have a low rpm stumble and I am wondering if this could be it. I just moved from Denver so I have been told that while the car is supposed to auto adjust for altitude I need to richen the mixture.. but I dont like stuff messed with like this.. fritz knew what he was doing when he designed the car I think..


Okay another question: the car while driving on the freeway seems to bob for and aft on bumps.. it does not exhibit a bounce like a damper is bad.. also pushing on the corners shows no bounce.. I don't like to "bob" down the road so how can I stop this madness? so its not bouncing in a corner.. its like someone is lifting the rear, pushing down on the front and visa versa.. I hate it and it must stop.

thanks guys.. sorry, I searched for the oil pressure stuff and just didnt see anything about the sender reading LOW oil pressure.. and nothing about bobbing for and aft..

[Gunter]

I would suspect the sender, not the gauge itself.
If a new sender is cheap enough, try it.

[calling911]

Originally Posted by Gunter

I would suspect the sender, not the gauge itself.
If a new sender is cheap enough, try it.

Either $42 or $67.. not sure which one I need yet..

if anyone has any answers for my other questions I'd be very grateful.

[javadog]

--the guages sometimes shake wildly which I will try and cure by cleaning up connectors..

Which gauges? The oil level gauge will fluctuate with oil temp, engine revs and over bumps. All of this is normal. If the tach is acting funny, you probably ought to service the distributor or check the voltage with the engine running. Dirty points and overcharging can cause the tach to act up.


--BUT.. last night while driving home in traffic I noticed when the temp gauge read 210 my idle pressure was nearly 0. at 2000 rpm it was oh around 15 (my gauge seems to read PSI not BAR)..

I'd check the oil pressure with an external gauge before assuming it's the sender. It could be several things, so start with the basics.

--then a little while later, still with temp reading 210 (is this oil temp?) ..

Yes.

--Also; why is my gauge in PSI? Is this unusual? This appears to be a california car..

That's what Porsche installed in the US 911S that year.

--Also; the advance vacum line is disconnected and plugged.. why?

Hard to say. Any other modifications to the car? Check the function of the distributor and check the timing.

--I have a low rpm stumble and I am wondering if this could be it.

Maybe.

--I just moved from Denver so I have been told that while the car is supposed to auto adjust for altitude I need to richen the mixture..

I'd have the fuel pressures checked and the CO reset, by someone that knows what they are doing and has the right equipment.

--Okay another question: the car while driving on the freeway seems to bob for and aft on bumps.. it does not exhibit a bounce like a damper is bad.. also pushing on the corners shows no bounce.. I don't like to "bob" down the road so how can I stop this madness? so its not bouncing in a corner.. its like someone is lifting the rear, pushing down on the front and visa versa.. I hate it and it must stop.

Some fore/aft pitching is normal in a 911. Are the torsion bars and shocks/struts stock? What type are they? Do you know if they are original or have they been replaced at some point in the car's life? Hard to diagnose without driving the car.

JR

[JohnKo]

Don't overlook the possibility that your gauge is displaying accurate oil pressure. <10 psi hot with no load isn't ideal, but it may not be that unusual (or especially horrible). What is it at 3,000 or 4000 rpm? At the risk of emphasizing the obvious, the 'rule of thumb' is ~1 bar (~15 psi) per 1,000 rpm.

Do you mean "bob" over bumps like a relatively stiffly sprung and relatively short wheelbase car? Just the way it goes. Shocks too stiff?

[gigem75]

more than likey the guage is accurate but you'll only know for sure checking with a known mechanical guage. Is the oil pressure significantly higher when the oil is cold? If it reads higher when cold and lower when warm chances are it's reading accurate.
How many miles on the car?

On my pre rebuild motor my pressure was right off the bottom at idle and around 40-45 at highway speed, 3k? Apparently it's no big deal and normal for the pressure to read low at idle on these motors.

[2.7RACER]

My best advice is to contact your local PCA club and ask about where to find "THE" Independent Porsche shop. The shop folks trust and use.

Have this shop do a "PPI" type inspection.

Check the suspension components, shocks, tie rods, A-arm rubber bushings, probably worn out, rear trailing arm rubber bushings, likewise probably worn out.

Brake pads, calipers, rotors, brake lines, change brake fluid. Wheel bearings, CV joints and the rubber bellows. Likely need to be cleaned and regreased at least.

Check system voltage, ground straps at battery and body to trans. Replace as necessary.

Thorough inspection looking for rust, particularly under and around the battery box, under the pedals, and where the front A-arms mount. A little rust found means there is more hiding.

With 180K on the odo there will be lots of things needing attention.

I would do a compression check and if any numbers are low, pull the valve covers and check the head studs and barrel nuts.

Use the thick silicon rubber valve cover gaskets with new washers and nylock nuts, low torque 8 lbs.

While the valve covers are off check the rocker arm gaps using the "backside method" Adjust as necessary.

Check the valve covers, especially the lowers on a flat surface. They tend to warp up at the corners and leak oil.

You need to understand what needs to be done first and prioritize.

The vacuum line retards the timing for smog purposes. You probably want it left as is.

At high altitudes ignition timing is usully set as much as 5 degrees advanced over what works best at sea level.

Mixture is set leaner at altitude so it "may" need to be richen up. Get it done right a Porsche shop with a sniffer.

There is more, much more. I'm sure others will chime in.

Good luck,

[Craig]

JP,
Lost of good ideas above. I have a 77, and it states in the owners manual that that the oil pressure will be extremely low at idle when warm. Mine was. I would not be alarmed at this. As mentioned above, does the pressure go up when you rev the throttle or at cruising speed?
As for the PSI gauge, mine is the same way, I like it as it makes more sense to me.
Good luck,
Craig

[eR1c]

oil level guage is shaky until you are at idle then it should level out after about a 1/2 minute to give you a reading of the oil level (although I recommend also checking the level manually periodically -via the dipstick while engine is warm and running).

Rest of guages should be relatively stable (no shakiness).

[Richard Burns]

My '77 shows very little oil pressure at warm idle and all of the people I have spoken to say this is normal. At cold idle I have 3 bar of pressure until the car warms up, I have a mechanic son who tells me "Dad worry about flow pressure means restriction". So to put my mind at rest and to stop p***ing my son off about it I changed to Mobil 20/50 dino oil. I still get a low reading at idle but not zero on the dash gauge.
Richard.

[calling911]

This turned out to be a flakey Oil pressure gauge/Sensor.. its just part of the charm

[T77911S]

porsche used different sized oil pump/scavenge pumps throughout the years.
it is not uncommon to 0 psi at idle on the early cars. my 77 is 10 to 15 psi at idle. but, when i run the RPM's up, the oil tank gage goes down as the tank drains. i often wonder how low the tank gets when driving hard and where all that oil is going.
my idiot light goes out after about 10 sec of turning over, it does not normally take that long to start.

i had stumbling off idle at one time too. someone told me to disconnect the vacuum to the distributor as yours is. mine ran worse that way, harder to start too. i hooked mine back up, reset the timing and mixture (the mixture had been adjusted by PO so i new it was not right, i am sure i am not at 3%, but it runs good. i will eventually have a sniffer put on it once i am sure everything else is right).
i just recently removed the distributor and using the wire brush on my bench grinder, i cleaned the outside of the dizzy ( i did this because when i would touch the dizzy when trying to set the timing, the car would cut off and then back on. the oxidation on the dizzy was causing a loss of ground). i also sanded the nut and washer and the surface on the block where the dizzy makes contact with it. the car is running better and starting better than it EVER has. no popping or backfiring during startup.

as far as the "bob", your front end could be too low and sitting on the rubber stops, or the struts are locked up.