Well's, here's what I think. I think the new sensor is probably a regular 4 wire sensor. When you changed it out it puts the ecu into a open loop mode, where it largely ignores most of the sensors and just runs it on the rich side of things. Consequently, it smoothed out the idle, but your not going to get any mileage worth anything.
If your really lucky, maybe he didn't cut the old sensor wires right at the nub of the sensor. If he left you 1/4 inch or so, then you should be able to reattach the old wiring and reinstall the old sensor. If you do and the sensor light stops coming on, then that's the problem. If you want to try replacing the ecu, their are 4 nuts which hold the cover on, under the passengers side floor mat. Remove the nuts, unplug the connectors, remove the ecu. Reverse with the replacement.
I wouldn't do anything additional, until you get it back to where the cel light is not coming on. Then, if you need to, get a sensor from a regular source and try it.
With a VX, their are some people who have had the idle issues you seem to be having, who have only been able to get it to work correctly by replacing the sensor with a new, authentic one.
At least the sensor should be removable, now, without doing anything to hard.
If I were the mechanic, my perspective would be that your bringing me the parts, my only responsibility is to install it. If it does or doesn't work, at that point is your deal, since your sourcing the parts. Like SVOboy said, you might as well just get some tools and start doing it yourself, instead of paying someone else to do it, for you. Good Luck
It's really weird how some VX's can use the $79 LAF sensor from Global-Automotive and some can't. Could it be that the Canadian ECU is set up differently than the 49 state ECU?
AND, it is always better if you are the mechanic. At least, you know who f***ed up and why!!!!! I wish "professional" mechanics had more training. I have had my share of headaches with them over the years.
Okay, I've counted the wires. So it's not a 4 wire o2 sensor. There are 5 wires. I took a photo of it somewhere.
It did NOT smooth my idle. It smoothed my acceleration. The idle has been high now when coasting in neutral, and drops only when I stop the car. Another thing I noticed, probably from bump starting today for the first time with the new o2 sensor is that the idle is now bouncing. 1000-1200 or something like that. It goes down to about 800 at a stop.
I want to be really clear about the Check Engine Light. It only comes on after one minute or after I turn the car on. It does NOT come on immediately upon starting the car. Furthermore, when I turned the car off for some engine off coasting, when I bump started, the light did not come on again. Not after one minute, not after ten minutes. I did three bump starts on the return trip and there was no problem bump starting. Now my question is, will the CEL come back on when I start the car again? I didn't test it because I really didn't want to see the CEL come on again during my ride home.
TomO, why do you think it is in "open loop"? Should there be some hesitation? No one has actually answered me ever as to how much hesitation is normal if any. Lot of VX owners out there. Some feedback on that would be appreciated. I do know that Canada (I believe) did say his car no longer has any hesitation issues with his new o2 sensor, which was the SAME o2 sensor as mine.
I guess the reason I'm a little agitated right now is, because, one, I'm stressed out about my mechanic cutting the wires (He didn't cut them at the nub, over an inch or so.)