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My dad has a 2008 Wrangler with a v6, automatic. The thing has no power, it sees a hill coming an starts slowing down :). We tried to use it to pull a car out of the ditch and even in 4 low it wouldn’t pull it out. The odd thing is it wouldn’t spin the tires at all either (maybe traction control??). Once we tried going up a steep grass hill and it did the same thing, no spinning, just not enough power to go any further.. It gets 11.5-12.5 mpg. I plugged a code reader in even though it didn’t have any lights on and it showed the long term fuel trim was +17.2 on bank 1 and +13.3 on bank 2 at an idle. When you hold the gas at 2500 rpm both drop to +/- 1. The other thing is on my reader it shows bank 1/bank 2 sensor 2 short term trim at 99.2, it doesn’t move no matter what you do. I am not sure if this is a function of the reader and there is no sensor 2 fuel trim or not? I tried spraying brake clean while at an idle around the vacuum hoses to see if I could find a vacuum leak, but nothing changed the idle. I did change the plugs and air filter with no change... any thoughts on where I could go next? Trying to help my dad but I don’t know a lot about jeeps..
thanks for looks and any comments!!
Dennis
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I don't have an old 3.8 with the auto trans. So keep that in mind.
The old 3.8 lacks the power of the newer 3.6. And the old 4 speed auto trans only makes it worse.
But in 4L you should have a reasonable amount of power, certainly enough power to spin the tires trying to pull someone out. And while traction control would / could stop that wheel spin, in 4L it should not.
To me it sounds like you have an issue with the automatic trans, not the engine. But it is hard to know what you mean when you say "no power". I assume you mean it simply would not pull, that could be an issue with the engine, but then it would run poorly all the time. And in 4L it should have enough pull to spin the tires going up a grass hill. Unless you weren't in 4L at the time.
Good luck. I hope someone with more direct experience with that engine / trans combo will chime in.
 

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It would not pull is correct, you could give it gas, the engine would strain, but not rev up and it wouldn’t move. It also lacks power during regular driving, meaning when you go up any incline even with it floored and the rpms up it will loose speed. Thanks!!
 

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No power for an 08 is subjective. However, in 4l you shouldn't have a problem spinning the tires on grass or being able to go up any hill. Does the engine bog down or are the RPMS there with no forward movement? Could be a transmission issue. If you want to reset the fuel trims and have the vehicle set back to stock so it can re-learn disconnect the battery cables and leave them off overnight or hold the pos and neg together for 30secs to discharge the pcm.
 

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Discussion Starter #8
I will check the tires/ratio tonight when my dad gets home. The Rpm’s do not increase more than 2500 or so, there is no slipping in the tranny that is audible/visual. It is just like even though you floor it the engine cannot pick up RPMs to spin the tires..
 

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So the trans is not kicking into a lower gear when floored? Sounds tranny related to me.
 

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That is a stock size tire for some Jeeps, but I don't know if that is what yours came with stock.
There are a few ways to determine the gear ratio. One is to enter your vin into a website that will pull up the build sheet for your Jeep. That works fine as long as no one has changed the gearing from stock.
Another way is to mark one of the tires at a fixed point, say at the 12 o'clock position, and roll the Jeep forwards one rotation of that tire and see how many times the drive shaft rotates for one rotation of the tire. That is your gear ratio. I taped a length of string to my drive shaft and counted how many times it wound around the drive shaft since I was doing it alone.
 

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If you have stock size tires then you probably have stock gearing which should work fine. I'll ask again - does the Jeep downshift into a lower gear when floored? Your rpms when floored should approach the redline before shifting into the next gear. Forget about focusing on spinning the tires because the 3.8 is a gutless slug to start with.
 

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Your short term fuel trim is likely too high, but you need to be looking at the long term fuel trim to get a better picture. You have to add the short term and long term together in order what you have. Just calling out long term at one time interval and short term at another doesn't give you a good picture. But when you see 99% that means the computer is giving as much extra fuel as it can but not getting the motor to respond.

Does the engine respond to throttle with transmission in park? Could be a plugged cat?
 

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Discussion Starter #15
The rpm goes up fine in park, you can redline it. In normal driving it will pickup rpm, it is just very slow to do it, I will see my dad this weekend and do a zero to 60...
 
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