Where is the orfice tube on a 96 chevy lumina?

If you look at the low pressure side line going from the dryer to the condenser you will find a crimped place and it is probably down by the condenser and that is where the orifice tube is.

They show a 5031 as being used in both model years. To change it though you have to pull the steering wheel off. This means special tools etc.

the engine block is the same but their are some changes such as sensors ---computer software -and in 1999 chevys been using dex cool the red coolant verses the green they are not compatible would need to do a flush before using engine but since you have a donor car should be able to do a swap just make sure you grab all and correct electronics with it

Could be a clog in the tube going to the EGR valve, or in the tube/hose leading away from it!

the fixed orifice is located in the inlet tube to the evaporator core, this is where the small high pressure AC line from the compressor connects to the tube sticking out of the engine firewall, u will most likely need a special tool to remove it, here is a web link to the tool, don't damage the evaporator core by trying to remove the orifice tube without this if it is stuck down in the tube.

http://www.google.com/products?hl=en&q=ac+orifice+tube+removal+tool&rlz=1R2ADBF_en&um=1&ie=UTF-8&ei=X4BETJiZC4-esQPw-ajJDA&sa=X&oi=product_result_group&ct=image&resnum=3&ved=0CCsQzAMwAg

the orfice tube is in line inside low side line near the accumulator in the enigine compartment (passenger side) remove the large nut at the accumulator and it usually can be extracted with needle nose pliers .If its crammed with debris from a compressor failure,there is a special extraction tool to dig it out

Here is a diagram of your motor with the firing order:

hi im wes the firing order is 123456 1 3 5 is on passanger side 2 4 6 is on drivers side