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O2 Sensor Downstream

RangerGoolz

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Howdy all. new to the forum here and also new to me is my 1986 ranger with 2.9. Here in Colorado I can register my truck as a classic and therefore emissions exempt. I am planning on new exhaust and removing the cats. My question is in regards to the 02 sensors. I know I need to leave the 2 upstream ones but what about the downstream? I am reading it wont hurt anything to disconnect but I wanted to ask the pros here before I dive into this project. Thanks so much and looking forward to learning a ton here.
74666
 


alwaysFlOoReD

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I dont think you have a downstream o2 sensor. I believe they weren't required until OBD2 in 1996?
 

RangerGoolz

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OH wow ok well thats even better. I guess I need to get under there and look. I am just reading up on buying new sensors and read there were three. I'm at work so i cant look now. Any other advice on going true duals and loosing the cats for a 1986 2.9 fuel injected?
 

alwaysFlOoReD

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Iirc there is only one o2 sensor in 86.
For duals I would put in a crossover and put the o2 sensor in that.
PS: that's a really sweet ride!
 

rumblecloud

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I've learned in my experience here that we don't usually discuss removing cats as it is in most cases illegal. However, in your case-- since it is legal-- the experts here might make an exception . I am not one of those experts, sooooo.....
 

alwaysFlOoReD

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Cats are a federal requirement by law.
 

RonD

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+1 ^^^

Cats are required in all states, federal law, up to $2,500 fine for individual, $25,000 fine for a Business/shop
Are there Cat inspections, not that I have seen, but exhaust shops may be hesitant to install or even work on an exhaust system without Cats as they could be on the hook for removing them or not reporting No Cats

1986 2.9l Computer only has connection for one upstream O2 sensor, if running dual exhaust you could put it on either banks pipe, but it would be "seeing" only that one side air/fuel mix balance
Original setup had the one O2 after the "Y" when both sides exhaust could be "seen" blended

I think the 2.9l computer got hook up for two upstream O2 sensors in 1990, when the 4.0l came out which had two

As said no Rangers had downstream O2s until 1995, the first year of the new EEC-V 104-wire computers, they had the extra connections for 3 or 4 O2s
 
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SenorNoob

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Early 4.0 still only had a single a O2. Mine does. It thinks it's a 92.

The engine was from a 93 and had just enough exhaust attached to see it was setup for 2 O2s.
 

gaz

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RangerGoolz,
The 86 2.9l has only one O² sensor; it was originally located on last ½' of the passenger side of the "H" pipe collector.

ADVICE/NOTE:
This stock engine will run GREAT with a single 2¼" exhaust, duals will be too much...if you perform a max torque rebuild on a 2.9l, it will run great on a single 2½" exhaust.

If you are dead set intent on a "true dual exhaust" then you are in luck as the 1986 features an "H" pipe after the exhaust manifolds which is perfect for duals, verses the later added "Y" pipe; however, the tubing is only 1½" so that is the largest I would use if I were to dual a stock 2.9l (which I would not).

Additionally, I recommend keeping the cat(s), I've rebuild the exhaust on both a 1987 Ranger and 1987 Bronco 2, several times, always keeping the cats and suffered no negative issues. In fact both those rigs get over 25 mpg in town, so I do not see any advantages to removing them.

If your exhaust needs replacement, there are free flowing cats available from many sources for under $100, so even the cost for a cat that may live for 20 years depending on your driving needs is relatively inexpensive. I use a 2 into 1 cat, with a single 2½ exhaust for my max torque rebuilt 2.9l, I can't imagine better results.

As a closing note, if you are replacing your muffler(s) I must recommend checking out the universal mufflers that BORLA has to offer. Their simple Turbo muffler performs great and has a nice, subtle sound. If you want more sound they offer several other models; their XR1 is so good it flows better than strait pipe!!!
 
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