Where are they located?

 

Usually located on the exhaust pipe ahead of the catalytic converters. So it could be right after the joint of the Y-pipe or on the inlet pipe to the cat. Some have a second sensor after the cat as well.

 

yes, look under the passenger side, near the oil filter, on the down exhaust pipe, between the pipe and the catalytic converter, there's the first one, I haven't found the second one yet.

also if you offer the Year and Engine Size of your van, it would help.

 

Normally Aerostar's have two oxygen sensors (Forward of the Cat and Rear of the Cat). Sometimes you need to use a propane torch to remove them.

Make sure the Oxygen sensor wiring is secured properly away from the drive shaft spinning.

 

OBD 1 vehicles (1995 and back) will only have one O2 sensor before the cat.

OBD2 vehicles (1996 and onward) will have 1 before the cat and one after solely to monitor catalyst efficiency.

 

yes, a sensor to sense the sensor.

 

You are right, and thank you for clarifying the O2 sensor issue for OBD 1 (1995 and back) Aerostar.

 

I replaced both O2 sensors in my 96 4l Aerostar and it was like putting in new spark plugs and wires. Absolutely Amazing.

I used OEM Bosch 02 sensors and it took less then 30 minutes, did not use the special wrench, just a crescent wrench.

Red the Aerostar was running just fine, no codes or anything. They were old so I decided to replace them. Wow! I was totally surprised at how much more power and smoother the engine was. Keep in mind it was running just fine before the change over. When I pulled them out they had some build up like spark plugs get a light brown or medium tan color. So they were working OK.

Also I am running Autolite Iridium spark plugs and now have over 15k on them and Red the Aerostar still starts like the day I put them in. In the past I found that regular spark plugs benefited from replacement every 10-12k. The motor would take longer to start in the mornings. I will keep you posted as the miles rack up on the Iridium plugs.

BTW I use the street version of the Iridium plugs rather then the ones for racing. I bought them with a rebate so total cost was like $3.50 each. A good deal when you consider how much work it is to replace these babies. Of course I put in new plug wires, PVC valve etc. at the same time. I have not checked the gas mileage and I did replace the rear end oil with synthetic fluid at the same time.