What did I do wrong? Please help!!!
 

I bought a 1996 elantra automatic gs wagon with 120,000 miles. I got the car a few weeks ago and it wouldn't stay started so I scanned it and got tons of codes. to fix all the codes i replaced the coil pack, spark plugs & wires, both O2 sensors, used (but fully functional) fuel injectors, oil change with filter, installed a coolant flush and fill kit, and a new radiator cap.

Here is were things went wrong: today I bought and installed the fuel injectors to correct the misfire on cylinder 2 but replaced all four just to be safe. I took the car out for a spin and it drove like it was brand new. on the way home i got gas. then i decided to install the coolant flush tee. i cut the line to the heater core installed the tee and went to drive the car over to the water hose. but when i started the engin, it could barely stay on. oh, i must add the exhuast was very cloudy had an odd smell. i decided to disconnect the battery and took the car on the highway. when i got back the exhaust was more normal but not perfect and the engine is now stumbling and low rpm's. So what did I do to what was a perfect car for 32 minutes?

I had a catalytic converter with a blockage at 60,000 mile on my 87 toyota tercel....it gave similar symptoms....good luck!