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Old 01-12-2013, 09:27 AM   #1
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Acceleration issues

When accelerating the 2007 jeep is fine up until 4000 rpm. After that, it just redlines and doesn't move any faster. Anybody know why?

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Old 01-12-2013, 10:31 AM   #2
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Manual? Auto? How many mile?

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Old 01-12-2013, 01:15 PM   #3
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Auto with 65,000 miles.
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Old 01-12-2013, 01:16 PM   #4
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Does it seem to shift normally?
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Old 01-12-2013, 01:22 PM   #5
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check your accelerator pedal 2007 are drive by wire i think? lots of snow and dirt problems
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Old 01-12-2013, 01:29 PM   #6
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Sounds like a transmission issue if it's not upshifting.
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Old 01-13-2013, 12:00 AM   #7
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It shifts normal (for a jeep)
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Old 01-13-2013, 12:02 AM   #8
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do you mean the tach just pegs itself or that you get no more acceleration after 4000RPM's

If it's that it just feels like it won't accelerate faster after 4000 it's because at 4000 the torque produced by the engine falls off a cliff.
See here:
2012 Jeep Wrangler JK - Trail Test - 4 Wheel Drive Magazine
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Old 01-13-2013, 01:47 AM   #9
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dIf it's that it just feels like it won't accelerate faster after 4000 it's because at 4000 the torque produced by the engine falls off a cliff.
So much so that speed ceases to increase completely? Not even 1 more mph? Wow!
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Old 01-13-2013, 01:56 AM   #10
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Sounds like you may have a catalytic converter that is plugged up. I had that problem in my TJ. It is possible that the ceramic element inside has broken up and possibly plugged the passage. My old TJ's cat rattled so bad I thought that I had a loose heat shield or a rock was stuck somewhere underneath.
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Old 01-13-2013, 10:54 AM   #11
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Have your Jeep scanned for codes.
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Old 01-14-2013, 03:00 PM   #12
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It might be the cliff that you are talking about because after 4,000 rpm it just makes more noise and doesn't accelerate any faster, it might even accelerate slower than at 4000 rpm
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Old 01-14-2013, 03:14 PM   #13
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Check to make sure you are not in 4 wheel lo. My dad did that on his Chevy recently and had the exact same symptoms. If you are in 4 lo I would not admit it to anyone. He has not and never will live it down.
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Old 01-14-2013, 04:56 PM   #14
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I am 100% sure that I am not in 4lo
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Old 01-14-2013, 05:24 PM   #15
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My guess is that you are out of power at 4000 RPM's. That is pretty much the peak of your power curve.
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Old 01-14-2013, 05:37 PM   #16
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Whoa there. I think the OP is saying that the RPMs keep climbing when accelerating past 4000 RPM but the Jeep doesn't go any faster with the increasing RPMs.

If that's what is happening, something in the tranny is slipping. Nothing to do with lack of power......
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Old 01-14-2013, 05:43 PM   #17
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I guess we need more info.

Are you crusing at 30 mph, you gun the engine, and the tranny slips above 4000?

Or are you already doing 75 mph, you gun the engine, it downshifts, and you are simply not getting much acceleration above 4000 rpms?
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Old 07-11-2013, 09:41 PM   #18
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Bringing the topic back up but it is usually when I am getting on the highway. I have to be very careful not to go much over 4k RPM's otherwise it will jump to close to redline and no longer accelerate. Then 1-2 seconds later after taking foot off of accelerater it will go back down in RPM's
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Old 07-11-2013, 09:46 PM   #19
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Originally Posted by 123Jato View Post
Bringing the topic back up but it is usually when I am getting on the highway. I have to be very careful not to go much over 4k RPM's otherwise it will jump to close to redline and no longer accelerate. Then 1-2 seconds later after taking foot off of accelerater it will go back down in RPM's
Sounds to me like your slipping at the torque converter...
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Old 07-11-2013, 09:53 PM   #20
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Sounds to me like your slipping at the torque converter...
agreed.

check your fluid for starters
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Old 07-11-2013, 11:26 PM   #21
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agreed.

check your fluid for starters
Which fluid are you referring to?
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Old 07-12-2013, 07:24 AM   #22
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From reading through your posts, you have the 42RLE mated with the 3.8 on 33" Micky Thompsons.

You most likely have 3.73's since you have a non-Rubi auto (but some non-Rubi had 4.10's in 2007).

Have you re-geared? Has your speedo been adjusted?


Basically, you are going to have to be heavy on the throttle to get to 4000 rpms with that set up (or the vehicle is doing a lot of downshifting), and there really isn't any more power beyond 4000 rpms.

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For you to be at 4000 rpm's on the highway, you have to be between 65 and 70 mph...and in 2nd gear. You will be at the speed limiter around the time you hit 4000 rpms in 3rd gear. I think you are just heavy on the throttle and running out of power.
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Old 07-12-2013, 08:22 AM   #23
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Which fluid are you referring to?
He's referring to transmission fluid.
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Old 07-12-2013, 08:25 AM   #24
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We need a video of what is going on.

I can't tell if you are talking about your tranny slipping above 4000 rpms, or if you are talking about a lack of power above 4000 rpms.
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Old 07-14-2013, 05:51 PM   #25
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It will accelerate up to 4k rpm, then it ceases to accelerate anymore after the 4k RPM's (no more mph increase). happens only when accelerating off a stoplight or getting on to the highway. ( I realize I am a little heavy footed) I realize that it is hard to explain
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Old 07-14-2013, 05:55 PM   #26
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It will accelerate up to 4k rpm, then it ceases to accelerate anymore after the 4k RPM's (no more mph increase). happens only when accelerating off a stoplight or getting on to the highway. ( I realize I am a little heavy footed) I realize that it is hard to explain
you accelerate, once it hits 4k the tach continues to increase while the vehicles speed does not?

slipping torque converter, thats really all it can be. the cause could be a few things, but most importantly, fluid level. if I remember correctly your dipstick should be in the engine bay starboard side of the engine.
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Old 07-14-2013, 11:04 PM   #27
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you accelerate, once it hits 4k the tach continues to increase while the vehicles speed does not?

slipping torque converter, thats really all it can be. the cause could be a few things, but most importantly, fluid level. if I remember correctly your dipstick should be in the engine bay starboard side of the engine.
You are correct, I will check the fluid levels tomorrow
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Old 07-15-2013, 06:26 AM   #28
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It will accelerate up to 4k rpm, then it ceases to accelerate anymore after the 4k RPM's (no more mph increase). happens only when accelerating off a stoplight or getting on to the highway. ( I realize I am a little heavy footed) I realize that it is hard to explain
Hmmm....

Is it doing anything else at all (besides no power above 4000 rpm)?
Surging or lagging of power?
Stalling at stop lights? (Unless you put it in park)
Tranny noise?
Are you have trouble shifting from park to drive, or into reverse?

It is hard to say if it is tranny problems, or if you have just maxed out the engine power. Few people have their Wrangler engines above 4000 rpms....at that level, you are at 100% of your torque, and 90% of your HP.

Can you confirm your axle ratio (3.73 or 4.10) and are you on 33's with aftermarket wheels?

And yes, check the tranny fluid. What color is it? Is it foamy?
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Old 07-15-2013, 12:18 PM   #29
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Hmmm....

Is it doing anything else at all (besides no power above 4000 rpm)?
Surging or lagging of power?
Stalling at stop lights? (Unless you put it in park)
Tranny noise?
Are you have trouble shifting from park to drive, or into reverse?

It is hard to say if it is tranny problems, or if you have just maxed out the engine power. Few people have their Wrangler engines above 4000 rpms....at that level, you are at 100% of your torque, and 90% of your HP.

Can you confirm your axle ratio (3.73 or 4.10) and are you on 33's with aftermarket wheels?

And yes, check the tranny fluid. What color is it? Is it foamy?
There are no other problems with shifting. The only strange thing I notice is when it goes over 4k it will stay there a couple of seconds even after I take my foot off the accelerator. The reason for such hard acceleration is because it is my dd and the spot to enter the highway seems to be very short compared to others so I have to work it hard to get up to speed.
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Old 07-15-2013, 12:37 PM   #30
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There are no other problems with shifting. The only strange thing I notice is when it goes over 4k it will stay there a couple of seconds even after I take my foot off the accelerator. The reason for such hard acceleration is because it is my dd and the spot to enter the highway seems to be very short compared to others so I have to work it hard to get up to speed.
Interesting...
Without seeing it, it is hard to say.

If the Jeep has shifted into 2nd gear, it might take a beat or so to upshift and find the right gear once you are off the skinny pedal....but it should not hang there for too long.

Can you give us a but more history on your Jeep? Which Sport is it (did it come with 29"'s or 32"'s)?

Is the axle ratio 3.73?

Are you on 33's? If so has the speedo been adjusted?

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