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Topic: Drop in MPGs but no check engine light????

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threeEs99
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Drop in MPGs but no check engine light????
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Ok in the last month or so. I've been noticing a big drop in mpgs. I talkin about 140ish miles on a tank.evileye  Now I would fix the problem but can not figure it out what is causing it. I have not changed my driving habbits, do not warm it up, rarely use the heater, tires are aired to 35psi and havent beat it on a trail since Aug. So I'm hopping you all could throw some ideas my way. I was getting 256 miles on a tank, every tank for the last year. HELP

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aci4369
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I would check the spark plugs, maybe one of them are fowled out.   Is it riding rough?  That is wierd though that it just started getting bad MPG.

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threeEs99
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New spark plugs a week ago, runs fine. The only other engine mod is my cold air intake. A cracked exhaust manafold would cause the CE light right? My wife has been driving it untill we get her ride back. She said it wouldnt start right away about a week ago , but it was raining and that dose happen sence I put in hood vents. I may go to Autozone to use a code scanner to check and reset to computer. See what happens than.confuse

-- Edited by threeEs99 on Thursday 19th of November 2009 07:35:12 AM

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PC
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probably would not get a CEL with a small crack in the exhaust manifold

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Defiance665
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I would also check your oxygen sensors, they may be bad or going bad and just havent set off a CEL yet.. Check and clean your MAT sensor too, if it is bad it will tell the computer its colder outside than it really is, causing a rich condition. What kind of exhaust do you have on it? Have you noticed any change in exhaust tone, throttle response, bogging down?

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threeEs99
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Defiance665 wrote:

I would also check your oxygen sensors, they may be bad or going bad and just havent set off a CEL yet.. Check and clean your MAT sensor too, if it is bad it will tell the computer its colder outside than it really is, causing a rich condition. What kind of exhaust do you have on it? Have you noticed any change in exhaust tone, throttle response, bogging down?


The o2s were replaced three years ago with bosh ones and I have checked those. However I have noticed a louder exhaust. I have a homemade cat back with no tail pipe so it was loud to start, but it has gotten louder. What is a MAT sensor?   

 



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Defiance665
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Manifold Air Temp.
I asked about the exhaust to see if you noticed it getting quieter or not. If it was getting quieter it could be a clogged exhaust. Since your saying its getting louder, I would check for a leak before the Oxygen Sensors..

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Jeep Guy
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how many gallons are you filling up each time? I ask this cuz when my fuel pump was going bad I was only able to fill up maybe 14 or 15 gallons. I replaced the fuel pump and can regularly fill up to 19 gallons.

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threeEs99
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Jeep Guy wrote:

how many gallons are you filling up each time? I ask this cuz when my fuel pump was going bad I was only able to fill up maybe 14 or 15 gallons. I replaced the fuel pump and can regularly fill up to 19 gallons.


I'm not sure, but my wife says she is filling it up.  I'll be able to drive it starting next Wed. after she gets hers back. All of the suggestions are going to be checked. Thanks. Keep them comming.

 



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tjhawk
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I am guessing you have winter blend at the pumps now which is 10% ethanol. This will cause a hit to your milage becasue the ethanol is not as potent as 100% gas.

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threeEs99
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I no longer have a MPG problem. It magicaly corrected itself. Checked for codes, nada. Filled up at same station I always do and now getting 258 on a tank. I did not do a thing. ???????? Went over completely and found only a bad wheel bearing. Hopefully replacing it will correct the wondering issue.

-- Edited by threeEs99 on Wednesday 25th of November 2009 11:24:41 PM

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Jeep Guy
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same thing happened to me. my wife was driving my Jeep for a while and it seemed it had bad mpg's. I started driving it again and all was better. hmmmmmm...... lol. glad to hear it's not an issue anymore. happy thanksgiving!

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threeEs99
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Jeep Guy wrote:

same thing happened to me. my wife was driving my Jeep for a while and it seemed it had bad mpg's. I started driving it again and all was better. hmmmmmm...... lol. glad to hear it's not an issue anymore. happy thanksgiving!


Glad to see someone caught this. I'm not blaming her, its just odd, eah?evileye

 



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99 sport.
rust bucket, DD, 3 car seats
04 wj (w/3 car seats too)
DD duty for the lady  
aci4369
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hahaha.  That is funny.  When my wife drives mine she is super cautious.  It is bigger taller and harder to control than her Rav... So I don't have that problem.  

But you know what they say about women drivers... Or should I just show you???







-- Edited by aci4369 on Saturday 28th of November 2009 01:30:14 PM

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'11 Dodge Charger

I miss the days that they made toys that could kill a kid.

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threeEs99
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Good stuff Andy. LOL x200
However in her defense her driving is great. Its her fear of being cold. See she thinks by starting the jeep a 1/2 hour before she leaves, that the heat works better. The kids are cold is her common excuse.
Jeep is running pretty rich again though. Burning your eyes rich. Seems to do so only at intinal start up, accompined(sp) by a chatering valve noise. I do think I have a broken lifter but has not been this loud ever. At 140k I wouldnt think ther would be any valve train issues or worn parts.

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99 sport.
rust bucket, DD, 3 car seats
04 wj (w/3 car seats too)
DD duty for the lady  
 
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