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1996 Ford Explorer with a 1999 Ford Explorer engine


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July 31, 2019
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Year, Model & Trim Level
1996 Ford Explorer
Hey all, so I’m having idle issues and check engine lights are always on. Anyways I’ve removed all the old o2 sensors to replace them and ran into and issue with the connectors not matching. I only have 3 sensors and can only hook up two of them. Found one just dangling there unhooked and figured that was my idle issue. When I took it out it was all wet. What’s going on?

Is it an issue with there being different connections between the year model difference or am I missing something? Here are so pictures I was able to snap. Thanks for your input!





More information please
It looks like you have a 96 explorer with a 4.0L V6 and auto trans
the engine was replaced with a 99 OHV?

You wanted to replace all 3 of your oxygen sensors but the place to install the 3rd one is MIA?
Or the wiring plugs for the 3 02 sensors will not plug in?
sometimes the aftermarket 02 sensors can require some wiring changes, or at the very least you have to shave off one of the little plastic nubs so it will fit the connector.

Please explain your situation with a little bit more detail
A 96 and a 99 Explorer with a 4.0 V6 should BOTH have 3 ea 02 sensor, 2 are upstream sensors, one for each exhaust bank and the other (3rd) is the downstream sensor
Your 3rd sensor is missing?
Was the exhaust replaced?

Yes the engine was replaced with a 99 OHV. Not sure if the exhaust was replaced, I bought this vehicle off a coworker for cheap and he mentioned the work done, but the engine swap was done by someone else he bought it off of.

I took out all 3 sensors, 1 was near the engine compartment and was plugged into the green female connector pictured up near the rear of the engine, the other 2 were downstream on each exhaust bank but neither was plugged into any connector. The grey female connector pictured wasn’t hooked into any of them which I noticed when I opened up the hole in the floor. And this grey connector doesn’t really take the green male connectors that weren’t plugged in. I did shave off one nub to see if it would fit but the connection didn’t really work. It was loose and fell apart. But the problem is that I need two plug ins where the one grey one is so that I can plug in my new o2 sensors when I buy them. Will that take a lot of rewiring to accomplish or can I easily splice the wires that are available to hook into both downstream sensors easily?

I’m guessing then that the exhaust was replaced as well as it doesn’t match what you are saying about 2 upstream and 1 downstream as mine are seem to be backwards.

I hope that makes more sense. Thanks for helping out.