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Discussion Starter · #1 ·
What is this connected to my IAT? This is a new to me 91 YJ with a fresh remanufactured long block, this was tied into the IAT when I bought the Jeep. I'm trying to trouble shoot what seems like a rich running engine due to 9.5 MPG and strong rich smelling exhaust while driving topless.
 

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Are there any identifying numbers on it? Whatever it is , it doesn't belong there.
Remove it carefully since those taps cut into the wires. See if you get any codes when it runs. Someone may have installed a fixed resistor to fool the computer.
If that's the case, it would account for the mileage if the computer always sees a cold manifold temp.
 

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What's with the plugged vacuum hose?
While you're cleaning things up, check the manifold fitting to the back of the valve cover. Mine was completely blocked with oil crud, keeping the engine from venting the crankcase.
 

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Yeah, I was thinking a fooler, too. For your "cold" air intake(?) perhaps
 

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Discussion Starter · #5 ·
There is NO numbers or letters on it. I knew it wasn't original equipment. As far as the plugged vacuum line, im slowly getting it back to original set up and I'll have to look into it. Codes that I have are 11, 12, 15, 22 and 33. I'm slowly working on those also, but this little black box caught my eye qickly.
 

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One of the best investments you'll make owning a YJ, is a Factory service manual.
There are some free copies on the web. Mudmagnet's sig line has a link to some of them. I have one on CD that lives in my drive bay for ready reference. CD version
 

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It's probably one of those ebay performance modules that were big on ebay right after the fast and furious movies came out.
 
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Do yourself a favor and remove the hot air intake and joke filter and reinstall the factory airbox. Remove the black fooler box. Reset your engine codes and see what happens.

"Performance" filters don't filter worth crap and the fine oil mist they exhale mixes with the dust they pass. Look for a brown grime in your intake and on that sensor

Since its new to you, throw a new O2 sensor on it along with all the tune-up stuff.
 

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That's pretty much what I was thinking about, going back to factory set up. I've got to see about OEM air filter box if I can find one!
The factory pays engineers plenty to figure out what works best on any particular vehicle.
Along comes a back yard mechanic and he says "I saw an ad on TV or the net that states that I can get better mileage, more power and the girls will like me better".
Once he buys it and installs it he says to himself, "I spent $X.00 on it and my seat of the pants tells me it's working great". (Especially if the vehicle ends up with a louder exhaust).

REALLY??

I think you are well advised to return your Jeep to factory configuration.

Will a Cherokee air box work? If you can get it to fit, they should be much easier to find.

Good Luck, L.M.
 

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The cops installed the black box to keep the criminal who owned it before from driving while under house arrest. Maybe I just saw it in a movie but it sounded good.
 
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