please help

[sergio318is]

having a few issues just purchased the car a few weeks ago 91 Alpine 318is and didn't pass inspection ( everything was fine exempt high hydrocarbons on normal idle was over 42 ppm)  on high idle it passed (with work haven't had time to make it to DMV for reinspection getting home late)  I have since did sea foam changed sparked plugs cleaned icv changed gas filter oil change air filter differential and have new o2 sensor to put in but can't get old one out. I know the its still stock exhausted and where cat connects to downpie right before o2 sensor the joint in rusted and my have bad seal/gasket.  also oil pan has leak hope its just lower but haven't had chance to drop it and change gasket. last few days when reaching stop rpms started to drop down to 600 for small secound  and go back to normal and stay fine. now when ideling it keeps going back and forth from normal idle +/-900 to 600.  it I gas it up to about 2000. it idle fines for few secounss then starts back up. and check engine is flashing for a while goes of and then stays on thegoes off

[DesktopDave]

Try the stomp test, might help out.  I'm thinking O2 sensor, but it's just a guess.  If your readings are that close it might do the trick.  Have the inspection station get a new one in...it won't be that expensive.

Your oil pan probably isn't leaking.  It's likely a gasket on the face of your motor like the cam PS or chain gaskets that's dripping down onto the pan.

Your check engine light might be blinking because the O2 sensor isn't heating up.  I had to use PB Blaster & a special socket to remove mine, they're never easy.

[pdxmotorhead]

To get a stuck O2 sensor out, break the harness and the tube off, (Big crescent wrench use the hole in the handle.) then a big socket fits on the nut part of the sensor.

A 20 gauge gun cleaning brush works good for cleaning the threads out, or a battery cleaning brush.

Dave