dr.stevil

So I just got this car a few months ago (June of '12). It's a low milage 2001 GT, 5 Speed. Got the car with approx 48K miles on it. Now it's got around 51K miles. For the most part, this car has been running perfectly... although have had a couple issues with the window switch and interior lights that I need to get to the bottom of. I also hear a high pitch whine from what I assume is the throwout bearing (from some reading I've done) every once in a while.

Anyway, so about 1.5 months ago the IAC valve started to go. On cold startup, occasionally, the car wouldn't hold an idle. I compensated by just giving it constant throttle (1K-1500 rpm) until it warmed up and fixed itself. Then I started noticing the oil pressure dropping when the RPMs would drop down (3-400 RPM's... if not lower, from the IAC going wonky). I'm not sure if the car always did this, and was just now noticing it, or if it's a 'new' problem.

So a few weeks ago, after unseccessfully trying to clean the IAC, decided to buy a new one from AutoZone. It went in with no issues and it immediately fixed the problem with the Idle. Unfortunately, it didn't fix the problem that I was having with low oil pressure. I picked up a new pressure sending unit but haven't had the chance to replace it yet.... although I don't think that it's the problem (I'll explain).

On a completely cold startup, the car idles fine (1200 RPM or so), engine runs smooth and life is good. However, once it gets warmed up, anytime the engine is sitting idle (about 6-700rpm), the oil pressure drops and the guage reads zero. The engine seems to run a little more rough (although, still not what I'd call terrible) and I can also smell the faint scent of burning oil.

If I give the throttle a slight blip, the oil pressure comes right back. Although, it's not always the same. One day I might have to bring the RPMs up to 8-900RPM and the oil pressure comes right back... other days I might have to bring the RPMs closer to 1600 and above to bring the oil pressure back.

I've checked the oil several times and everything looks okay. The level is fine and I haven't seen any debris in it. The car isnt leaking anything either. I don't beat on it or drive it like a jerk so I'm at a loss what could be wrong.

I'm hoping that the dealer I got the car (hyundai dealer) from is using a thinner oil than the car calls for and hence, the low oil pressure... but I'd like to be certain. I have yet to change the oil yet, so I'll be doing that next weekend.

With all that said, does anyone have any ideas or theories as to whats wrong? Anything that I can check for thats not going to cost me an arm and a leg? I got rid of my GTO for this car, hoping that it would be more reliable, but something tells me it's going to turn into a money pit

cliffyk

It is most likely that the oil pressure switch (it is just a switch, not a real sensor/sending unit) is bad. The o/p switch closes when the oil pressure is above 6 psi, and opens when it falls below 6 psi.

The gauge is just a pretty "idiot light", when the o/p switch is closed it goes to its mid-range more or less--though sometimes the indicator may come to rest in slightly different positions.

The recommended oil is 5W-20, you can't get much thinner than that. FWIW and many will argue this, in NY I would run 10W-30, unless you are way upstate it's winter...

dr.stevil

thanks for the reply.

I'm aware that the oil pressure isn't necessarily a real guage, but what concerns me (and why I'm thinking that it's not the sending unit/sensor) is the rough idle, smell of burning oil when the pressure is down and the pressure not dropping until fully warm.

All of those things have me worried that the car may have been abused at some point, and the bearings are starting to slowly fail.

I'm going to attempt changing the sensor/sending unit on Sunday, so hopefully that takes care of the issue. I'm nervous that it wont though

FrostByte

If you want to remove all doubt install a gauge (under hood or inside cockpit) that reads actual pressure.

I think u need to adjust the idle screw on end of throttle cable/linkage or your TPS voltage. There are specific instructions on how to adjust it properly.

Here is a vid that may help. How to reset your TPS voltage.

dr.stevil

Thanks for the reply. So I had my doubts that it could be the sensor, as I smelled burning oil when the pressure dropped, leading me to believe that something was probably wrong internally.

Anyway, i had a chance to check it out today and to my surprise, the sensor and the immediate area around it were wet, coated with a thin sheet of fresh oil. So i pulled the old one out and installed the new one (very easy to get to btw) and was surprised to see the plastic o-ring on the old one completely shredded, although i think thats what its supposed to do. Im guessing that once the oil heated up, it got thin enough to slightly blow past the threads and cause the sensor to act up. And the smell of burning oil was that hitting the oil pan or something else under the car.

So I took it for a spin, let it get up to temperture and it held steady. No burning oil smell, no pressure drop... Everything ran great. With that said, thanks for the help and checking this thread out. I really appreciate it. Feels good to have the car 'right' again.

Heres a pic of the old one btw
http://db.tt/tAjzlxdt

http://db.tt/vSEl1TPc