trys to die at stop light

[Bain64]

hey would a bad o2 sensor cause bad cat code?

Is it possible? Yes. Is it likely the problem? no.
Follow advice above first.

 

[TobyU]

hey would a bad o2 sensor cause bad cat code?

Rarely. If you're talking about a ln 0420 or 0430 code for catalyst is below threshold efficiency... it's rarely an oxygen sensor. Usually a sensor is just fine and doing its job and just reporting back the conditions that are out of spec.
These two are usually caused my ignition misses, unburnt fuel, or burning oil.
Sometimes the converter has been damaged a little bit and is weak other times it is fine. If you have occasional random misfires from the coils and plugs not being in the best of shape then the unburnt fuel will prevent the converter from cleaning up and making the mixture as clean as it should be when the second O2 sensor senses it.
You can use a scan tool to check for test results and see the misfire counts for each cylinder to see if the cylinders on bank 1 or bank 2 coincide with the converter code you're getting for Bank 1 or bank 2. Remember Ford bank one his passenger side unlike other brands.
Sometimes coils and plugs will solve the problem and the converter code won't come back. Other times it will sometimes it takes a month or more. At least it has for mine on some cars taking a long time to pop back up. But it will not make the car run badly at all. The converter code itself will not make the car run badly and you won't even be able to tell if there's any running issues but, sometimes certain things causing the converter code to pop in the first place will make the engine run rough or miss.

 

[TobyU]

I just reread your original post. You've got to get the large vacuum leak fixed first because with a vacuum leak the engine richens the mixture trying to make up for it and there's extra fuel that can be unburnt causing your cat code.
Get the vacuum leaks slow down to a minimum then clear and recheck codes. Then I would check for misfire accounts and feel if you have any shaking your vibration at all of the engine with it in drive with your foot on the brake.
The EVAP leak or any other vacuum leaks are going to cause it to run poorly and get worse gas mileage.

 

[johnboneske]

I strongly doubt it's an O2 sensor. Why not figure out the cheapest fix first, which is a vacuum leak, yes you need a smoke machine but after that it cost a few dollars for some rubber hose. You have had other codes as I remember, it all points to vacuum lines. Once it is fixed, it will smooth out at idle, won't want to quit, etc. A bad O2 sensor may throw a code but have never had my SUV run like crap with a bad sensor, plus changing the O2 sensors is a pain in the ass! Check the vacuum lines!

 

[TobyU]

The vacuum leaks also seem to be worse when temp is below 40.

 

[Bruce Mitchell]

With 235K you may have a cluster of vacuum leaks. I recently had heater core flushed, left the shop, got a mile down the road and saw steam coming from under the hood. Back to the shop, mech went to fix coolant leak - as he was working on that fitting (which disintegrated in front of both of us), the vacuum fitting behind it fell apart. He fixed that. Two days later the engine light comes on - codes for both O2 sensors bad. Was running fine, cleared codes, couple of days later engine light back on - codes for both banks too lean. And a misfire popped up from nowhere (and it didn't want to idle). Back to the shop - mech found and fixed bad PCV valve elbow fitting and another vacuum leak way down at the bottom back of the engine. Been running fine for a month now.

SO, start simple and work your way up. It's that Occam's Razor thing.