1999T/A

iTrader: (4)

I have a problem with my car and I am not sure if it might be the oil pump or maybe the cats. I read about the O-Ring going bad on the oil pump so it could be that I have multiple problems here. I do have the same symptoms as the bad ORing , except that my oil pressure never really makes it to 20psi , more like 27Psi or so . The ticking is very loud and it used to come and go , but now it is here to stay . I noticed when I was driving it home that when I give it throttle , the oil pressure goes down , and when I let off the throttle , it goes back up ! WTF ?!?!?! Could clogged cats pressurize the engine to the point that it fights the oil pressure ? I have very little exhaust coming out of the tailpipes , i have to put my hand right up to the tailpipes to feel the exhaust gases ( approx. 1 inch away ) . Also , when giving it gas while cruising , it acts like I didnt give it any gas ! Kinda bogs down . Weird . The cats dont get red hot and the car doesnt cut off . What do you guys think ?

TIA ,

Joe

robertbartsch

Take the cats off and look inside; if they are melted you will know.

1999T/A

iTrader: (4)

Ok , I will check that out this weekend if it doesnt rain . Will clogged cats pressurize the engine to where it will make the oil pressure drop? I am thinking the car would cut off before that happens . Anyone that has had clogged cats have their oil pressure drop when you give it the throttle ?

1999T/A

iTrader: (4)

TTT ! Anyone have this happen to them before ????????


Thanks in advance ,


Joe

jimmyblue

iTrader: (11)

I don't believe you can melt the substrate (which is
either zirconia or alumina, very high temp ceramics).
Before that, you will trash the catalyst plating layer.
Once the catalyst is gone the cats will no longer rise
above exhaust port EGT (cats go overtemp because
the chemical reactions they perform, further add to
local exhaust temp).

The only way to clog cats it to be coughing out more
lung-butter than they can crack - !AIR could aggravate
this by delaying or preventing proper light-off, gross oil
burning is bad too as the long-chain oil is tough to fully
burn and to crack by catalytic combustion, not to
mention all the heavy metal crap that rides along in
the oil.

But oil pressure should not respond to throttle position.
It should be purely RPM based. It is unlikely, and just
wrong, that throttle position, cylinder pressure or
exhaust pressure should affect the oil pressure.

I think it's more likely that the problem is sensor based,
such as a missing block ground strap and a block ground
voltage that's no longer zero relative to PCM / chassis
ground. Try measuring the voltage between block and
fender, block and TPS black wire (PCM ground), with
some variations like A/C on/off.

Not to say that the oil pump isn't bad or its O-ring, but
the response to throttle is abnormal. Oil pressure should
respond only to RPM.

If the ticking is louder with throttle position that's more
likely an exhaust leak and exhaust leaks can corrupt your
O2 readings and mixture control.

CHRISPY

If you have knocking and variance in oil pressure you likely have spun a bearing. You'll need to pull the motor.

1999T/A

iTrader: (4)

This isnt a knock , it is a tick ( coming from up top , not from the bottom of the engine ) , and it used to come and go , but now is here to stay . It came back running about 55 mph in 6th gear at about 1200 RPM . The last time it started ticking and went away was around the same RPM , under very similar conditions . Jimmyblue , thanks for that answer , it sounds to me more like the oil pump is grenaded now more than anything . I am tearing into it his weekend to see what I can see . It made the same ticking noise one day when it lost spark on #6 cylinder , due to a worn out plug wire . After that , it went away , only to return after i replaced the wires and found the PCV hose had a big hole in it where it connects to the intake/throttlebody . The symptoms it is having though is exactly what the symptoms of a bad oil pump/ ORing is , so I guess I will start there .

Thanks fellas ,

Joe

jimmyblue

iTrader: (11)

Might check the valvetrain, especially for rockers
that have lost their roller bearings or bent pushrods.
This you can do from the top. Neither should have
any big effect on oil pressure (though maybe some
added internal weepage).

That's some peculiar cascade of problems. You got
'possums living under the hood?

1999T/A

iTrader: (4)

Yeah thats what I get for buying a 150K mile LS1 car . I knew I should have bought one with less mileage , but at $8000 , and the car is mint from top to bottom , I thought I got a good deal . Now Im broke and my car is messing up.

Chris , take it back man ! Take it back ! It can't be a rod bearing ! LOL !!

Kyle C

I have a Chevy truck that did the same thing, oil pressure went down when I push the gas. Changed the oil pressure sending unit and it acts as it should now.