check engine light is usually an emission problem. bad cat or o2 sensor or could even be a gas cap. i think on that year they only had one 02 sensoe in front of the cat,so the cat can be bad and an 02 sensor should fix. it isn't unusual for the engine oil pressure to read zero on a warm engine on a toyota. what is the oil pressure when driving warm? the ticking could be normal on that model. the rear diff could be going out but that isn't a biggy. doesn't sound like you have head gasket problems to me because it isn't blowing coolant out of the radiator. i would bet you can make a good driver out of it pretty cheap once you get in the right forum.
tranny shifting problems could be a bad speed sensor. get her scanned.
Toyotas don't need oil pressure. They are blessed from the grease of Gods. The ticking is only to let you know they are there. If they are knocking, it's on heavens door.
HAHAHA! How true. My Tacoma V6 with 329K on it sounds like a singer sewing maching when I got it. Thought WTF is that ticking noise? It still does it.
Oh My God! "the grease of gods" that is funny. I have two land cruisers with over 200k. they both idle warm engine zero on the oil gauge,but that doesn't mean they have no oil pressure. all that means is the gauge isn't accurate below 15 lbs. if you think it has zero OP then you should confirm with a mech gauge.
Thanks guys i am learning more and more about the nuances of 4runners. I about had them all down for Cherokees. I am leaning more towards the cat. The exhaust on this thing sounds like a damn abrams tank. I did a little research on other forums and it is possible that the cat is bad. When it heats up to operating temp the cat is expanding and is clogged or something to that effect. So a trip to american discount mufflers on 15th and sheridan (free plug to some good guys) is just around the corner, then off to Harmons 4 wheel drive (another plug for the small guys doing aswome buisness) to check the rear end. I think the ticking/knocking i am hearing get louder as the oil gauge drops is either paranoia, or the exhaust is gettinv louder and rattling more as it warms up.
Great. the nice things about most Yotes is you can fix as you go on most stuff. they will run broken when most will be in the ditch. just a little John Deere tape and you are good to go.
The ticking could be due to an exhaust manifold crack. I've seen that before with the 3.0. http://www.toyota-4runner.org/4th-gen-t4rs/93178-exhaust-manifold-leak-tick.html
I'm with Jason on this, an exhaust leak at the manifold can sound a lot like a lifter rattling
