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Unread 12-16-2014, 08:29 PM   #1
mudcrwsr
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2001 TJ Wrangler 
 
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Possible cure for poor gas mileage

Hey all I wanted to post some information I learned recently.

Flash back a few months... I'm on a wheeling trip with some friends in the NC mountains and I'm rolling back home on I40 and get to Raleigh. Suddenly the temp sensor rockets to 260 in the red. Luckily, traffic was thick and slow and I was in the far right so I could pull over and shut the motor off. Result, cracked radiator core in my Drake off-road radiator (4 months out of warranty and SOL). I managed to limp the jeep home with a few extra bottles of coolant, and once I got home I decided to replace the entire coolant system (Radiator, fan clutch, water pump, thermostat and coolant temperature sensor). The jeep was also throwing a P303 code (#3 injector is bad etc) which it had been doing all summer long, so I also decided to replace it along with the other injectors. I opt'd to use the local auto store vs. OEM/stealership for all parts as it was way cheaper. Plus ACDelco offered lifetime warranty on parts... kind of a no brainer for me.

So now to the meat of all this. After replacing everything the she was back on the road. Everything was running fine, but I noticed I was getting horrible gas mileage. (160 mile on a full tank.. 19gal. IL6). At first I thought it was the injectors or maybe fouled plugs but after checking this wasn't the case.

After doing some diagnostics on the sensors, eliminating intake/exhaust gasket leaks I noticed my running temps were somewhat low (180-200 registered). From this I deduced that I had a bad control temperature sensor and t-stat. Even though they were new, they were not up to spec from OEM and were giving a false reading.

This was one of the few times I went to the stealership and bought a new t-stat and TCS. Come to find out with both being bad/not up to oem spec the sensors were registering a cooler running motor, as a result the engine was staying in an open loop mode which made the motor run rich as it was trying to warm up continuously and this resulted in burning more fuel, fouling plugs etc. and poor gas mileage. After replace both the TCS and the t-stat with Mopar OEM parts the jeep is back to running at 210. The heat is hotter in the cab and mileage is back to what it was (which wasn't great) but I am at least back to 260-280 miles on a full tank which is where I was before.

Just wanted to share if any of you have done something similar or may suddenly be having issues with poor mileage.

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Unread 12-16-2014, 08:49 PM   #2
Thedawgshow
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Right on and thanks for sharing!!!
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Unread 12-16-2014, 11:00 PM   #3
Knuckelhead
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Not bad for a software geek...
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Unread 12-17-2014, 10:21 AM   #4
StrokerJeep00
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I'm having the same issue with my 4.6L stoker......seems I need me some OEM Parts.
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Unread 12-17-2014, 10:54 AM   #5
mrblaine
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Quote:
Originally Posted by mudcrwsr View Post
Result, cracked radiator core in my Drake off-road radiator (4 months out of warranty and SOL)..
First off, thanks for the fairly clear cause and result on the rest of it but this part has me confused a bit.

Do you know from something else failing that the overheat killed the radiator or did the radiator dying cause the overheating?

I know it happens both ways so just trying to clear that up.
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Unread 12-17-2014, 10:56 AM   #6
mrblaine
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Quote:
Originally Posted by StrokerJeep00 View Post
I'm having the same issue with my 4.6L stoker......seems I need me some OEM Parts.
I use a lot of NON OEM parts, there are some that I won't substitute for aftermarket and those are the Thermostat, sensors, water pumps, and radiators. I need it to work the first time every time.
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Unread Yesterday, 10:10 AM   #7
mudcrwsr
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Quote:
Originally Posted by mrblaine View Post
First off, thanks for the fairly clear cause and result on the rest of it but this part has me confused a bit.

Do you know from something else failing that the overheat killed the radiator or did the radiator dying cause the overheating?

I know it happens both ways so just trying to clear that up.
For clarification. The radiator died which caused the overheat. Basically the inner core cracked at the top of the radiator passenger side. The crack was small but under pressure it basically forced the coolant out. It was only a matter of time before I basically drained/emptied the radiator while driving that weekend. When I did overheat, and pulled over the radiator was bone dry. I've got about 120k on the jeep and since I was going to replace the radiator (again) I thought it would be a good opportunity to go ahead and replace the entire system. Last thing I wanted was to replace the radiator and then have to go back in and replace the pump, or something else that failed from age etc. Plus having the radiator pulled made swapping the other components a breeze.
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