My daughter has an 01 with an automatic and 140k, she is having a problem that every so often when she pulls up to a stop, the engine will start to studder and then just dies. Wait a moment and it restarts without any further issue, no CEL showing. I thought that it may have an issue with maybe a catalytic converter that could be pluged, then when I got under to look I find that it has 4 converters and 4 o2 sensors. Why 4? If I changed this to a 2 cat system then what do I do with the rear o2 sensors? Also, it looks as if one of the rear catalytic converters has been replaced at some time.
Catalytic Converter question??
- Thread starter 8T9BlackLX
- Start date
wmburns
SN Certified Technician
The Mustang (and many other cars) use a pre-cat O2 sensor and a "after cat" O2 sensor. The pre-cat O2 sensor controls air/fuel mixture. The after cat O2 sensor is to monitor the working of the cats. The rear O2 sensors do not affect driveability.
The Mustang also uses what Ford calls a "light off" cat. This is followed by a regular cat. The purpose of the light-off cat is to allow any unburnt fuel to flare off before getting to the 2nd cat. The light-off cat is not harmed by higher temperatures.
If the light off cat were not present, the 2nd cat could have a short service life due to excessive temperature.
So in answer to your question. The rear O2 sensors are needed to monitor the cats (regardless of how many). If the rear O2 sensors are removed, a MIL will result (unless action is taken).
A suggestion, take it to a muffler shop and ask their opinion and get an estimate. It may not be as bad as you think.
FWIIW, for an automatic transmission car, dying coming to a stop could be a lock up torque converter not releasing as it should. Especially if the car idles fine in neutral.
The Mustang also uses what Ford calls a "light off" cat. This is followed by a regular cat. The purpose of the light-off cat is to allow any unburnt fuel to flare off before getting to the 2nd cat. The light-off cat is not harmed by higher temperatures.
If the light off cat were not present, the 2nd cat could have a short service life due to excessive temperature.
So in answer to your question. The rear O2 sensors are needed to monitor the cats (regardless of how many). If the rear O2 sensors are removed, a MIL will result (unless action is taken).
A suggestion, take it to a muffler shop and ask their opinion and get an estimate. It may not be as bad as you think.
FWIIW, for an automatic transmission car, dying coming to a stop could be a lock up torque converter not releasing as it should. Especially if the car idles fine in neutral.
