Acceleration Troubles

[bvahlberg]

Hi! I’ve been having acceleration problems for about 3 months now - 2005 TJ 4.0L automatic. All O2 sensors and spark plugs have been replaced. I’ve replaced all the front u joints (they were already needing to be replaced). I replaced the valve cover gasket - had a minor leak. My throttle body was removed and cleaned thoroughly - zero problems there. I’ve had suggestions that it could be my exhaust manifold or my head gasket - but I am not having any symptoms of either going bad - no smoke, no bad smells, no overheating, no rough idling, no loud noises or clanks or squeaks. The only problem I’m having is slow acceleration with high RPM’s and a lot of vibration during acceleration. It goes away once I get up to constant speed limit or I’m off the gas pedal. It’s especially bad going uphill. It happens cold or hot, doesn’t seem to make a difference. Thank you for any help!

 

[Chris]

Is it throwing a check engine light? If so, what codes is it throwing?

 

[EJD]

My throttle body was removed and cleaned thoroughly

Hmm, makes me wonder if when the TB was removed there is a possibility that the TV cable got stretched a little. You could inspect your throttle valve/kickdown cable to see if it was stretched at all and if so make the necessary adjustment to be at the correct tension. That would account for the slow acceleration issue, I once had the feeling my 4.0 lost some pep after my engine swap and it was due to the TV cable being pulled out ever so slightly. Corrected that and it made all the difference.

I do not have any ideas on your vibrations though...that could be a whole different can of worms.

 

[bvahlberg]

Is it throwing a check engine light? If so, what codes is it throwing?

It’s not throwing any check engine codes.

 

[bvahlberg]

Hmm, makes me wonder if when the TB was removed there is a possibility that the TV cable got stretched a little. You could inspect your throttle valve/kickdown cable to see if it was stretched at all and if so make the necessary adjustment to be at the correct tension. That would account for the slow acceleration issue, I once had the feeling my 4.0 lost some pep after my engine swap and it was due to the TV cable being pulled out ever so slightly. Corrected that and it made all the difference.

I do not have any ideas on your vibrations though...that could be a whole different can of worms.

What exactly is the TV cable? I wasn’t the one that cleaned the throttle body, because I’ve never encountered that before and didn’t want to accidentally damage something in the process. This is the first car I’ve owned that I’ve actually put work into myself, so I’m learning as I go. Thank you!

 

[xxdabroxx]

slow acceleration with high RPM’s and a lot of vibration during acceleration. It goes away once I get up to constant speed limit or I’m off the gas pedal.

Is your transmission slipping?

 

[bvahlberg]

Is your transmission slipping?

I’m gonna say no. All of my fluid levels are totally normal, and nothing is mixing. The RPM’s are high, but never higher than 2800-3000.

 

[John Scoggins]

Could be worn engine and/or transmission mounts, especially the trans mount

 

[xxdabroxx]

What O2 sensors did you use?

 

[billiebob]

Plugged cats ??

My TJ would not rev past 4K rpm climbing a grade and forced me to keep down shifting.

 

[bvahlberg]

What O2 sensors did you use?

All NTK sensors.

 

[LJBean]

Plugged cats ??

My TJ would not rev past 4K rpm climbing a grade and forced me to keep down shifting.

I've had the same experience as billiebob. Might have the cats checked out.

 

[EJD]

What exactly is the TV cable? I wasn’t the one that cleaned the throttle body, because I’ve never encountered that before and didn’t want to accidentally damage something in the process. This is the first car I’ve owned that I’ve actually put work into myself, so I’m learning as I go. Thank you!

Check out this video, it kind of describes what i'm talking about a "little" better. Bad video, but it looks to be the same throttle body and TV cable situation as our 4.0, shows how to reset the cable and could be the fix your looking for.

 

[Oldguy]

Easy way to check for plugged exhaust is to remove the upstream o2 sensor, it will be loud but will fee up the exhaust if it is clogged

 

[AjRagno]

The 42RLE does not have a TV cable, so it's not that.

You posted last month that you had P0153 and that you had also been in an accident and had the rear suspension rebuilt. Did you get the code resolved and have you verified that the rear wheels turn freely and the brakes are not dragging?

Can you confirm your gear ratio and tire size?

For the vibration on acceleration, I would suspect the rear driveshaft u-joints or the rear pinion angle is too high. The pinion will rotate up during acceleration, even more so if the control arm bushings are worn.

 

[MtnRanger160]

Looking for help, glad I found this thread. I replaced my valve cover gasket and happened to notice....I don't have a TV cable connected to the bell crank like the throttle/cruise cable. Am I supposed to have one? I have the 6-speed manual trans in an '05. Jeep has always had slow acceleration and got better when I put 4.56 gears (33" tires) in it.

 

[Duner]

I’m dealing with the same thing and I am stumped! 03 2.4L btw

Initial symptoms I noticed were a very infrequent “pop” noise that was coming from the passenger side engine compartment. If I had to guess these pops were backfires, which became more frequent. I then started having rough idle and acceleration. Without changing anything the backfires and rough idle went away, but sluggish acceleration hasn’t.

No check engine lights.

Here is a list of everything I’ve tested/replaced.

- spark plugs
- upper O2 sensor with NTK
- test run with lower half of exhaust disconnected at manifold (plugged cat test)
- test run with both O2 sensors disconnected
- fuel pump and filters. Did not replace regulator at top
- TPS sensor
- Cleaned throttle body
- checked fuel injector spray pattern


I think all there is left for me to do is look for a bad ground or check the exhaust manifold for a leak?

I’m open ears to anything else I can try.

 

[Jerry Bransford]

Here is a list of everything I’ve tested/replaced.

- spark plugs

Your 2.4L engine has a waste spark ignition system, exactly what brand and model # spark plugs did you install? Some supposedly correct spark plugs, per some spark plug guides, will cause problems like that. Single-tipped platinums to be exact. Single-tipped meaning they have the platinum coating on just one side of the gap which is what causes problems for waste spark ignition systems.

 

[Duner]

Your 2.4L engine has a waste spark ignition system, exactly what brand and model # spark plugs did you install? Some supposedly correct spark plugs, per some spark plug guides, will cause problems like that. Single-tipped platinums to be exact. Single-tipped meaning they have the platinum coating on just one side of the gap which is what causes problems for waste spark ignition systems.

Champion 7570 is what I used. PO had champion 3570 platinum. If I’m remembering correctly, I was having these issues before I replaced the plugs. I’m going to pull them to see how they look.

Edit: plugs look fine

 

[Jerry Bransford]

Double-tipped Platinums like the 7570 work fine with your waste spark ignition system.