Oil pressure/gauge spazzing out

fliphkd7 · 06-06-2007, 01:40 PM

Alright, I'm cruising down the road in my 89' S2. I glance at the oil pressure gauge to make sure I'm getting good lubrication. It's at like 4-5 psi(or whatever unit); normal. However, I push in the clutch to coast to a stoplight. The pressure then drops correspondingly with the rpms back down to like 3 psi; also normal. Then, it the gauge needle starts flicking, not unlike a dog wagging it's tail. During its episode, the needle never drops below the correct idling 3 psi, But goes all the way to the gauge's max. Any thoughts?
-When the accelerator is pressed, normal pressure resumes, ending the needle's wagging.
-My problem doesn't seem like a problem, I suppose the engine is just getting extra oil at idle?
-Faulty gauge, sending unit, or oil pump?

Icey1174 · 06-06-2007, 01:48 PM

Mine does the same thing. Bounces on the 3, but not all the way up to 5 at an idle, just a slight bounce, maybe 3.5. You'll have more oil prusure under a load. Sounds like it is normal to me. Unless I have some crazy problem too! I have heard of people going as low as 2 and 1 at idle.

fliphkd7 · 06-06-2007, 01:51 PM

I have a feeling it's the sending unit.
-Yeah I suppose as long as it never drops too low it's alright

BeerBurner · 06-06-2007, 01:52 PM

Mine has been doing that for years. I cleaned the connectors on the sender and the grounds but that made no change. I've given up on worrying about it.

BB.

fliphkd7 · 06-06-2007, 05:19 PM

Where is the sending unit?
-possibly it is a split wire some where in between..44's are notorious for electrical issues

BeerBurner · 06-06-2007, 05:22 PM

Gah... if I remember correctly, it's somewhere underneath the oil filter mount. You'd have to get to it from underneath the car. Look for two wires with the little thumb tightener thingies on it.

At least that's how it is on mine... not sure if the S2 is the same.

BB.

legion · 06-06-2007, 06:05 PM

My 951 does and my 944S did the same thing. I never worried about it.

dmilzoff · 06-07-2007, 03:52 AM

When the two wires from the oil sensor are connected to each other or one wire shorts to ground, the gauge will to to max. You may have a short either in the wires or the sender.

rudidelange · 06-07-2007, 04:15 AM

When the oil is cold it will show 4.5 - 5 at idle, mine drops to 1.5 bar at idle when the oil is hot - (after 15 kms, ambient temp is 30 degrees celcius, 10w 40 oil). When the ambient temp drops to 0 - 5 degrees celcius then it take hard driving for 20+ kilometers before the pressure will drop to 1.5 bar at idle. Thicker oil (20w 50) gave me approx 2 bar under the same conditions.

fliphkd7 · 06-07-2007, 07:02 AM

Yeah it's probably just a short, judging as how it seemed to get worse as the day progressed.

JustinL · 06-07-2007, 08:04 AM

You can test it with a friend if you have your electronics on. Have one person sit in the car and watch the gauge while the other guy crawls underneath and starts wiggling wires. I think they go from the sending unit, which is right near the PS pump- behind the belt covers- to under the intake manifold. If you peg the gauge with the engine not running, then you've found the short.

fliphkd7 · 06-07-2007, 08:28 AM

I just pulled the wheel and looked at the sending unit. It's covered in grime, etc. It looks alright, but I'm, going to do the test JustinL described.
-How are the wires connected to the unit? Bayonet and sheath type? The wires pass through a 90 degree rubber boot

hpaulb · 06-07-2007, 08:37 AM

On the sending unit, one wire is ground reference and the other is a resistive output. One has a nut and the other has a slip on spade lug. Both are covered with a rubber hood. Pressure wash the area to get rid of all the grime. The wires feed up through the front under the belt cover between the water pump and go under the intake manifold to the rear then into the large bundle.
Stick an ohm meter on the resistive lead and measure. That should narrow down the sensor ground, sensor itself or after in the wiring/ Gage.

JustinL · 06-07-2007, 08:39 AM

They are little washers nutted on to threaded posts. I think it's a 7mm wrench you need. Mine had just vibrated loose so a good cleaning and tightening solved my jumpy gauge.

fliphkd7 · 06-07-2007, 08:54 AM

Okay cool i'll be right back...

fliphkd7 · 06-07-2007, 09:05 AM

The connectors are all clean and have good contacts. I'll start it up here in a few minutes after I finish up my brakes to see if the problem still persists.

onZedge · 06-07-2007, 10:45 AM

Quote:

Originally posted by hpaulb
On the sending unit, one wire is ground reference and the other is a resistive output. One has a nut and the other has a slip on spade lug. Both are covered with a rubber hood. Pressure wash the area to get rid of all the grime. The wires feed up through the front under the belt cover between the water pump and go under the intake manifold to the rear then into the large bundle.
Stick an ohm meter on the resistive lead and measure. That should narrow down the sensor ground, sensor itself or after in the wiring/ Gage.

One wire is for the low oil pressure idiot light and the other is for the gauge. The ground reference is through the threads of the pressure port.

fliphkd7 · 06-07-2007, 08:57 PM

I drove the car after cleaning up the sensor posts. Still flicking. I did find that when I go over bumps/let the the clutch chatter the gauge freaks out. Therefore, the problem must be a short somewhere in the electrical line. The new sending unit is only like $30 from pelican parts, so I'll probably just switch it while I'm under there.

MixMasterK · 06-10-2007, 09:55 PM

Let us know what happens after you switch it out. Mine jumps while driving between 4 and 5 bar. It also flickers at idle. If switching it out solves the problem, then I'm going to do the same.

In a related topic, my fuel gauge won't read full after filling the tank. I've cleaned the brass connectors on the gauge cluster, but that didn't help it.

Kris

Icey1174 · 06-11-2007, 05:45 AM

My fuel gauge doesn't make it all the way to the full line either.