How can I find out what replacement engine is in my car?

[Jalic]

I got a 93 Civic cheap for something to play with. I need to change the O2 sensor in it. But, the car has a replacement engine in it. How can I tell what the engine is, so I can get the proper sensor?

[AudioGuy93DelSol]

All the honda 4-wire O2's are the same but to see what engine you have, look to the left of the exhaust manifold, under the upper radiator hose. There is a number like D15b7 or K20A - That number will tell you what engine you have.

[Jalic]

Ah. Thank you. Looks like I have a D16Z6.

EDIT

Oh, one more thing. Does the O2 sensor simple screw out? Is there any trick?

EDIT #2

I was looking at this page, http://www.troublecodes.net/honda/, and something caught my eye.

High idle speed, erratic idle when cold.

Intake air temperature sensor disconnected or open intake air temp. circuit. Faulty intake air temperature sensor.

That's what the car is doing. A shop said the error code being given is for the O2 sensor, and that could cause the problem. The previous owner put an afterwarket air intake on it, and it looks like there is a place to plug something in. Could the intake sensor simply be unplugged? I know, seems like a dumb question, but this is why I got the car to work on, for the experience. I didn't see anything hanging loose from the wiring harness.

Edit again

Ok, upon further inspection, I noticed something. The part in the picture (that I found online) that's circled in red is not connected. My car also has an aftermarket intake. Instead there's a small filter over the connection onthe top of the motor. It's looks like it's disconnected because the stock tubing wont fit the aftermarket intake. Also, the blue X shows where on my car's intake there is a connection slot for something, but nothing is plugged in. Could that be the problem? I'm trying to give as much info as I can.

http://img341.imageshack.us/img341/5545/enginehq3.jpg

[AudioGuy93DelSol]

A faulty O2 won't cause cold idle problems as the computer does not take readings from the O2 untill the engine is at operating temperature. O2's, if they are original, are practically impossible to get out. The best way is to heat the base of it, where it screws into the manifold, with a torch. Then try to take it out. Good luck.

That hose in the picture is your PCV breather. It doesn't need to be hooked into your intake, unless you need to pass a visual emmisions test. Also, that hole in your intake wouldn't cause the idle problems. If you have the fluctuating idle problem (up down, up down) read this for a likely fix.

[Jalic]

Here's a better explaniation of what's happening. When I start the car, it idles high, about 2k. After a little bit (a minute or less) it tends to bounce (go up and down) between 1.5k and 2k. I drive it for a few minutes, then at a stop it will idle low, about .2 or .3k. After a couple more minutes of driving, it will idle real low and stall out, and not want to start again.

I'll check out the FITV when I have time this week between school and work. Unless it sounds like I have a different problem.