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Old 03-21-2013, 06:21 PM   #1
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So Confused?

Okay I bought a 2002 tj a while back. The engine light was on but it sounded find so we bought it. I have only been getting around 11mpg so I thought it was the 02 sensors. Well I took it to a shop and they ran the codes. They said it was the thing to control how fast the heater heated up. He sounded like he really didn't know what it was and that it befuddled him. So my question is it could still be the 02 sensors? There's only 52,000 miles on it and its all stock. I feel like i should at least be getting 15 mpg. I will try to get the exact code tomarrow.

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Old 03-21-2013, 06:38 PM   #2
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If you just got the vehicle and don't know the previous maintenance schedule I would give her a tune up. Plugs wires new cap and rotor, fresh oil, new air filter. If its still throwing a code find out what the code is and repair it. And the mechanic sounds like he was talking about air charge temp sensor but I feel like ur truck would be running like crap it adjusts your fuel ratio depending on the air temp outside

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Old 03-21-2013, 06:48 PM   #3
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If the previous owner screwed up & installed a lower temperature thermostat than the factory specified 195 degree thermostat, the computer may be keeping the engine in its full-rich warm-up mode much longer (or all the time) than it should be. That can totally jack the mpg potential as well as hurting general engine performance. Some people think it's better to install a cooler thermostat but it's not & the engine and computer both require the right model 195 degree thermostat for the engine to run properly in all conditions.

So when he mentioned something about how fast the "heater" warmed up, that made me think he was actually talking about the thermostat. I would remove the currently installed thermostat and replace it with a 195 degree thermostat just to be sure.
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Old 03-21-2013, 07:00 PM   #4
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Okay thanks for the quick replies. From what he said on the phone it does sound like it is the air changer temp sensor. But it runs fine which I dont understand then. Are these sensors expensive or cheap enough to replace and see what happens?
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Old 03-21-2013, 07:07 PM   #5
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if possible post the actual code from the check engine light and some others who may have already had this code can chime in.
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Old 03-21-2013, 07:19 PM   #6
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Okay thanks for the quick replies. From what he said on the phone it does sound like it is the air changer temp sensor. But it runs fine which I dont understand then. Are these sensors expensive or cheap enough to replace and see what happens?
I've never heard of an "air changer temp sensor". What DTC (diagnostic test code) is causing your Check Engine light?

Did you read my above post where I discussed the engine thermostat?
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Old 03-21-2013, 07:43 PM   #7
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I never had the issue in my jeep but the sensor tells the computer the proper fuel ratio depending on the temperature of the air intake, sometimes a dirty air filter will throw the code too
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Old 03-21-2013, 07:59 PM   #8
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Could he be referring to "heated o2 sensor"??? You need the diagnostic codes he retrieved. Out of curiosity with the CEL light on why wouldn't you have had it scanned before you bought it? You could have used that info to negotiate the price.
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Old 03-21-2013, 08:00 PM   #9
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There is an IAT (Intake Air Temperature) sensor that is threaded into the intake manifold, perhaps that is what you are talking about. But unless the engine thermostat is assisting the engine to get up to its normal temperature, that IAT is only going to report the engine is too cold to go into Closed Loop mode (non-rich fuel condition) if the engine thermostat isn't the correct 195 degree model.
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Old 03-21-2013, 08:25 PM   #10
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If you just got the vehicle and don't know the previous maintenance schedule I would give her a tune up. Plugs wires new cap and rotor,
2000 and newer don't have plug wires, cap and rotors. Its a distributor rail and boots. OP has an 02.
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Old 03-21-2013, 08:29 PM   #11
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I couldn't think of iat but if you search parts at part stores they call the (iat) an air charge temp sensor but it could def be related to the thermostat, replace it like jerry says and if Its still doin the same thing then I'd change the sensor
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Old 03-21-2013, 08:36 PM   #12
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WWJD...... What would Jerry do? Believe.
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Old 03-21-2013, 08:46 PM   #13
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So should I replace the thermostat or the sensor? I'm even more confused now. I also a got a steal on the price and either I bought it or the other guy who offered more than what he was asking would of got it.
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Old 03-21-2013, 08:50 PM   #14
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You really need to find out what the code is and post it. Any other symptoms besides low mpg?
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Old 03-21-2013, 08:52 PM   #15
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Any Auto Parts store has a code reader, just stop by and get the code reader. This will diagnose your problem. We can speculate all day, but the code will tell the truth in about 30 seconds + the time it takes you to get to the store.

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Old 03-21-2013, 09:00 PM   #16
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2000 and newer don't have plug wires, cap and rotors. Its a distributor rail and boots. OP has an 02.
A "distributor rail"? Never heard it called that.
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Old 03-23-2013, 03:09 PM   #17
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Sorry for not posting the code yesterday. I went to the shop right as they closed. Anyways I got it back today and it ended up being a vacuum line and the 02 sensors. The bright side is that it only cost me 70 bucks but I don't think I will go back to that place. I'm a little disapointed in this guy who did my work.

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