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Thermostatic Air Temperature Sensor

S

SPVFD47

NAXJA Forum User
Location
South Plainfield, NJ
Anyone know where I can get one... its the little vacuuem valve in the Throttle Body cover. I hate calling the dealer and you'd figure Napa would have it but I can't find it on their site and the store doesn't open till 8 am tomorrow.
 
90 YJ and 90 XJ. If you pop off the throttle body cover where the air intake connects to its in there. Theres 2 small vacuum lines that plug in there, 1 off the main vacuum feed and then the 2nd goes to the air box that controls a vavle that opens air off the exhaust cover. I've seen the setup on a few various years and motors.
 
Last edited:
are you talking about these?
renix01b.jpg
 
Jeepsloth said:
are you talking about these?
renix01b.jpg
Click to expand...

That little dingus is the thermostatic vacuum valve for the "intake pre-heater" - the duct that goes down off of the airbox snorkel goes to a sheetmetal surround on the exhaust manifold, which preheats the air going into the engine. It's supposed to decrease warmup times (I'm not sure it does) and reduce emissions (it doesn't.)

Having it not work won't cause you any trouble at all. The moving element is a bimetallic strip that moves the valve "open" below a certain temperature, and "closes" it above that point. If it were a carburetted engine, it might be helpful (they do prevent carburettor icing,) but it's pointless on a PFI engine.
 
Jeepsloth said:
this is the dingus you're referring to Jon?
renix03b.jpg
Click to expand...

That dingus is the actuator for the door. It's little more than a diaphragm with an operating rod.

The dingus on the back is the one that turns vacuum on and off to the dingus in the second picture (don't you just love this technical talk?):lecture:
 
Yup, the valve is what I need. My actuator works fine. I do remember now that some have them inside the airbox. My old XJ was like that. I've been been toying with alot of things that I've read about in the FSM. Quite a few sensors and things seem to be bad on my YJ. The mileage isn't as great as it should be... Little by little its been going up and its getting cold here in North Jersey so I'm trying to see if works too. It can't that much for something little like that.
 
I've only seen it as a part of the airbox. I might have a spare airbox around somewhere, but I'd have to look.

Honestly, tho, you don't really need the thing. I've not had any trouble with the thing being long disconnected (including driving in the Rockies and northern Indiana in the wintertime...) since I can't honestly be arsed to get a new flexible duct for mine. And, if it were really that important, I'd not have passed smog checks without it, either.

Now, if I could just talk them into letting me delete the EGR - I've got reports done on their equipment that shows the engine runs cleaner without it...
 
The one on my '90 preheats the intake air charge to reduce the amount of fuel enrichment required during open-loop warm up mode. The ability to run leaner during warm up reduces HC emissions and provides a modest benefit to fuel mileage. Having it not work wouldn't keep me from driving to work Monday morning, but when it comes to emissions and fuel mileage, the little things add up.

Is it pointless? I doubt the Jeep engineers were so dumb, or had such a large budget that they put pointless parts on the 4.0.
 
In reality, it helps prevent "carb icing". In dry climates, it is not a problem but back east, when the humidity is high and the temps around 40, it can be a real problem.
 
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