MIL extenders for cat removal

Michael Yount

Mustang Master
Apr 10, 2002
Charlotte, NC
I've got a buddy who I'm helping engineer a 5.0L Mercury Moutaineer/automatic tranny swap into a 940 Volvo sedan. This model has O2 sensors upstream and downstream of the each cat - 4 in total. I believe this is similar to the set up you guys have on the mod motors.

What are the implications of removing the cats with this set up? Check engine lights? Drivability issues? And, the MIL extenders (is that the right term?), how do they work? I assume it alters the output signal of the rear most O2 sensor to fool the computer into thinking that the cat is still there. Do they plug in between the sensor plug and the harness plug? Who makes them - contact info would be great. Need to find out if they have an application for the Explorer/Mountaineer application. Thanks in advance for any help.
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Mr Yount, I have had nothing but problems with all of the MIL elims I have used. the check engine light has come right back on after 200 miles or so. I have used 3 different types from different retailers with no luck, check engine light for o2 sensors, go figure. No power loss just CEL. I am fairly confident with the knowledge you bring to the table that you will be able to work this out. there is a guy near me that made his own for his mod motor and swears the CEL has never shown its ugly face since then. Good luck to ya :nice:
Thanks for all the experiences - both good and bad. We'll give 'em a try and take it from there. Another more appropriately powered Volvo hits the road soon....

Given it's Mercury heart and soul - we're calling it the VOLVARAUDER.