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-   -   Acceleration issues (http://www.wranglerforum.com/f274/acceleration-issues-211308.html)

123Jato 01-12-2013 09:27 AM

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?

jkjeeper06 01-12-2013 10:31 AM

Manual? Auto? How many mile?

123Jato 01-12-2013 01:15 PM

Auto with 65,000 miles.

SilverSport 01-12-2013 01:16 PM

Does it seem to shift normally?

Lduggins 01-12-2013 01:22 PM

check your accelerator pedal 2007 are drive by wire i think? lots of snow and dirt problems

MikeK46 01-12-2013 01:29 PM

Sounds like a transmission issue if it's not upshifting.

123Jato 01-13-2013 12:00 AM

It shifts normal (for a jeep)

Doctorsti 01-13-2013 12:02 AM

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

MikeK46 01-13-2013 01:47 AM

Quote:

Originally Posted by Doctorsti (Post 3221818)
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! :rofl:

chuck_tempe 01-13-2013 01:56 AM

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.

SilverSport 01-13-2013 10:54 AM

Have your Jeep scanned for codes.

123Jato 01-14-2013 03:00 PM

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

redskinswin 01-14-2013 03:14 PM

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.

123Jato 01-14-2013 04:56 PM

I am 100% sure that I am not in 4lo

panthermark 01-14-2013 05:24 PM

My guess is that you are out of power at 4000 RPM's. That is pretty much the peak of your power curve.

Up Hill Bill 01-14-2013 05:37 PM

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......

panthermark 01-14-2013 05:43 PM

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?

123Jato 07-11-2013 09:41 PM

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

KurtVW 07-11-2013 09:46 PM

Quote:

Originally Posted by 123Jato (Post 3952728)
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...

Tweak 07-11-2013 09:53 PM

Quote:

Originally Posted by KurtVW (Post 3952740)
Sounds to me like your slipping at the torque converter...

agreed.

check your fluid for starters

123Jato 07-11-2013 11:26 PM

Quote:

Originally Posted by Tweak (Post 3952772)

agreed.

check your fluid for starters

Which fluid are you referring to?

panthermark 07-12-2013 07:24 AM

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.

(3.8 in black)
http://image.fourwheeler.com/f/roadt...ower_graph.jpg

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.

KurtVW 07-12-2013 08:22 AM

Quote:

Originally Posted by 123Jato (Post 3953135)
Which fluid are you referring to?

He's referring to transmission fluid.

panthermark 07-12-2013 08:25 AM

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.

123Jato 07-14-2013 05:51 PM

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 :)

Tweak 07-14-2013 05:55 PM

Quote:

Originally Posted by 123Jato (Post 3961770)
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.

123Jato 07-14-2013 11:04 PM

Quote:

Originally Posted by Tweak (Post 3961780)

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

panthermark 07-15-2013 06:26 AM

Quote:

Originally Posted by 123Jato (Post 3961770)
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?

123Jato 07-15-2013 12:18 PM

Quote:

Originally Posted by panthermark (Post 3963530)

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.

panthermark 07-15-2013 12:37 PM

Quote:

Originally Posted by 123Jato (Post 3964474)
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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