Crazy, Erratic Oil Pressure (with videos)
 

Yes, it's another oil pressure question. I've already searched thoroughly, but have yet to find another thread with these exact symptoms.

The problem:
My oil pressure gauge is going crazy from RPMs of 1500 - 2000 (it occasionally occurs out of that range but is consistently replicable within 1.5k to 2k). This happened both before and after i experienced a blocked catalytic converter.

here's a video I took today
http://www.youtube.com/watch?v=BewiSH5wcNA (smooth - on road)
http://www.youtube.com/watch?v=nKu043AtAp8 (bumpy - on road)
Yes, the hand-brake switch is effed. You'll notice if you watch the vids. I'm not driving with the brake on.

several months ago, blocked cat.
http://www.youtube.com/watch?v=q_66JueX0GY

It's a '95 z28 with an autozone rebuild. the engine has less than 20k on it, everything else 175k... it's mostly stock, except for a K&N CAI, smooth elbow, and holley airfoil. I'm running Mobile1 5w-30 and a fram tough-guard filter.

Additional information:
It's also had a fresh PCV valve installed (one week ago). Vacuum hoses are a little corroded, but a quick inspection shows them to be relatively solid. Nonetheless, at WOT I'm getting a lot of reverse oil-flow from passenger side VC to TB. This was determined by pulling the TB and seeing plenty of oil in the intake. Also the aforementioned hose is pretty oily most of the time. You can smell it at WOT.

The crazy oil pressure indications don't seem to correspond with the reverse flow problem, and it runs like a champ throughout. I don't know if these three are related or not (blocked cat, crazy oil pressure, reverse flow). The interesting part is, it's not consistent throughout rpm, or engine load which would seem to rule-out blow-by. It will do the same in neutral.

If any of you have experienced anything similar to this, your advice will be much appreciated. Oh, and no I haven't hooked up a mechanical oil pressure gauge yet.

Here's what she looks like:
http://i25.photobucket.com/albums/c6...404-1630-s.jpg

Possibly a "flat" spot on the winding of the sensor. Have you hooked up a mechanical gauge to see if its acts the same way?

The oil in the line to the throttle body may be indicating excessive blowby on the piston rings. Since you've verified the PCV system operation, its a bad sign.

An aside... the "BRAKE" light serves two functions.. 1) tells you the e-brake is on, or 2) tells you there is an imbalance in the hydrauic pressure between the front and rear brake lines. How did you determine the light is on because of the e-brake swithc being bad?

Thanks for the quick reply.

I haven't hooked up a mechanical gauge yet, but I will for sure.

As for the brakes, I know the rear brakes are working, but I can't speak to a hydraulic imbalance. I guess it's time to bleed 'em? I assumed it was the handbrake because the previous owner spilled a sugary drink right on top of the handbrake well. Hmm... sounds like further investigation is needed.

I think the sensor is frigged.

Lol...not that your problem is funny, but.......

I would like to call that a craaaaaaazy gauge. :D Prolly bad sensor man. If not, I don't know wth your car is doing. Especially shooting up that high, I think it's unlikely it's actually doing that. I believe the sensor is driver's side of the oil pan. Maybe pull it and replace?

The oil pressure sensor is not in the oil pan. Its on the top edge of the block, just behind the edge of the intake manifold (mid-94-97). The sensor in the oil pan is the level switch. No "pressure" in the pan.

Courtesy of Shoebox:

http://shbox.com/1/oil_pressure_sensor.jpg

http://shbox.com/1/op_sensor.jpg

Yeah its real easy to replace if you have the special deep socket. Takes 2 minutes.

Injuneer:
As your name implies, you pretty much know all here. :) Ha! My bad! I was wondering what that one on the engine block was, too. Now I know what they both are!