LOST JEEPS :: View topic - hesitation at cruising speed

My liberty seems to hunch and hesitate between decel and accel. It pulls strong on acceleration and it is smooth on deceleration but at that point of just cruising along with no strain at all on the engine and I am just giving it enough pedal to maintain speed, it seems like it wants to hunch or jump. Anyone ever had this issue before? What could it be?
Thanks,
Steve

TennesseeCRD wrote:

That is how mine felt before I got the GDE tune, herky and jerky feeling, cruising between 55 and 60 MPH.

Sounds like air in fuel to me...

If your fuel filter has more than 18,000 Miles on it, it may need to be replaced.

A clogged filter will deprive the high pressure fuel pump of fuel.

During high fuel demand (high speeds) the fuel filter has to be airless and filled with fuel so that the fuel pump can suck in as much fuel as it needs during peak demand and not take in any air along the way.

If the fuel filter is dirty and clogged, it will starve the fuel pump of fuel causing a Limp mode.

If air is in the system and especially in the fuel filter head it will cause a limp mode.

First and foremost replace the fuel filter and see what happens. Then maybe install a simple lift pump to keep the fuel filter filled to the brim with fuel continually supplying the high pressure fuel pump during peak demand (the time when the gas pedal is pushed down to the metal).

If you haven't already done so, replace the original fuel filter head with the new updated OEM fuel head, the old fuel filter head has been known to cause problems with air leaks and fire.

This is just a layman’s explanation and I hope it helps.

I am realizing that as time goes by and more issues arise with this little beast of a vehicle that I love, I am being lead to become a second class diesel mechanic through correspondence learning and this board, whether I want to or not.

Keep us posted.

Racertracer

Steve,

Try unplugging the MAF sensor on the airbox. This will cause a CEL, but it also shuts off EGR. This may be your light load hesitation issue. If the hesitation disappears, then the EGR system is showing the early signs of clogging internally.

You state the problem occurs at very light throttle conditions. Any chance it is 'slop' in the driveline (u-joints, CV joints)? With our tune we modify parameters that effect the torsionals at light load and when the pedal is released to reduce the driveline clunk. If it is just a light load issue, chances are it would not be related to fuel. Have you check the codes on the CRD?

I may be wrong but it doesn't feel like a trany or tc problem to me although I have been wrong before. It feels more like a fuel problem of some sort. Pulling out from a dead stop it is great but as you get to cruising speed and let off of the pedal some I can feel it start to hump. It is good in pulling and deceleration but just feels funny when no strain at all is on the engine. I wander what the problem was that the GDE tune fixed? Did you get the eco tune?

To the OP, I hope that you figured out the problem with your hesitation at cruising speeds. I just developed the same thing this weekend and I took it to a local tranny shop and they just scratched their head. I figure that it is either air in the fuel or the TC giving up the ghost. I did just change my fuel filter last week, but it ran fine after pumping the head. Any help would be greatly appreciated.

Author:	TennesseeCRD [ Sat Oct 30, 2010 10:17 pm ]
Post subject:	hesitation at cruising speed
My liberty seems to hunch and hesitate between decel and accel. It pulls strong on acceleration and it is smooth on deceleration but at that point of just cruising along with no strain at all on the engine and I am just giving it enough pedal to maintain speed, it seems like it wants to hunch or jump. Anyone ever had this issue before? What could it be? Thanks, Steve

Author:	CATCRD [ Sun Oct 31, 2010 10:06 pm ]
Post subject:	Re: hesitation at cruising speed
Sounds like torque converter shudder.

Author:	warp2diesel [ Mon Nov 01, 2010 6:14 pm ]
Post subject:	Re: hesitation at cruising speed
Transgo and Sonax both have parts to fix a bad front pump. Before I installed my SunCoast/Transgo upgrade, I tortured my stock converter with my experimental TCM that shifts at much lower RPMs. I never had the Shudder problem and when I put the Transgo kit into my front pump and valve body, the valve that causes the problem was good, but I replaced it anyway. I would not replace a bad Torque Converter with out fixing the valve in the front pump or replacing the pump, but if you love Casinos and win a lot, try your luck. Your call on that one.

Author:	flman [ Tue Nov 02, 2010 8:39 am ]
Post subject:	Re: hesitation at cruising speed
TennesseeCRD wrote: My liberty seems to hunch and hesitate between decel and accel. It pulls strong on acceleration and it is smooth on deceleration but at that point of just cruising along with no strain at all on the engine and I am just giving it enough pedal to maintain speed, it seems like it wants to hunch or jump. Anyone ever had this issue before? What could it be? Thanks, Steve That is how mine felt before I got the GDE tune, herky and jerky feeling, cruising between 55 and 60 MPH.

Author:	TennesseeCRD [ Sat Nov 06, 2010 9:58 pm ]
Post subject:	Re: hesitation at cruising speed
flman wrote: TennesseeCRD wrote: My liberty seems to hunch and hesitate between decel and accel. It pulls strong on acceleration and it is smooth on deceleration but at that point of just cruising along with no strain at all on the engine and I am just giving it enough pedal to maintain speed, it seems like it wants to hunch or jump. Anyone ever had this issue before? What could it be? Thanks, Steve That is how mine felt before I got the GDE tune, herky and jerky feeling, cruising between 55 and 60 MPH. I may be wrong but it doesn't feel like a trany or tc problem to me although I have been wrong before. It feels more like a fuel problem of some sort. Pulling out from a dead stop it is great but as you get to cruising speed and let off of the pedal some I can feel it start to hump. It is good in pulling and deceleration but just feels funny when no strain at all is on the engine. I wander what the problem was that the GDE tune fixed? Did you get the eco tune?

LOST JEEPS http://www.lostjeeps.com/forum/phpBB3/

hesitation at cruising speed http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=56561	Page 1 of 1

Author:	nalu [ Sun Nov 07, 2010 12:46 pm ]
Post subject:	Re: hesitation at cruising speed
Sounds like air in fuel to me...

Author:	TennesseeCRD [ Fri Nov 19, 2010 10:20 pm ]
Post subject:	Re: hesitation at cruising speed
nalu wrote: Sounds like air in fuel to me... Will this ever work its own way out or do I need to bleed it? This has been going on for a while now (2 months). Shouldn't it have worked its way out by now?

Author:	racertracer [ Fri Nov 19, 2010 11:20 pm ]
Post subject:	Re: hesitation at cruising speed
If your fuel filter has more than 18,000 Miles on it, it may need to be replaced. A clogged filter will deprive the high pressure fuel pump of fuel. During high fuel demand (high speeds) the fuel filter has to be airless and filled with fuel so that the fuel pump can suck in as much fuel as it needs during peak demand and not take in any air along the way. If the fuel filter is dirty and clogged, it will starve the fuel pump of fuel causing a Limp mode. If air is in the system and especially in the fuel filter head it will cause a limp mode. First and foremost replace the fuel filter and see what happens. Then maybe install a simple lift pump to keep the fuel filter filled to the brim with fuel continually supplying the high pressure fuel pump during peak demand (the time when the gas pedal is pushed down to the metal). If you haven't already done so, replace the original fuel filter head with the new updated OEM fuel head, the old fuel filter head has been known to cause problems with air leaks and fire. This is just a layman’s explanation and I hope it helps. I am realizing that as time goes by and more issues arise with this little beast of a vehicle that I love, I am being lead to become a second class diesel mechanic through correspondence learning and this board, whether I want to or not. Keep us posted. Racertracer

Author:	TennesseeCRD [ Sat Nov 20, 2010 10:23 am ]
Post subject:	Re: hesitation at cruising speed
racertracer wrote: If your fuel filter has more than 18,000 Miles on it, it may need to be replaced. A clogged filter will deprive the high pressure fuel pump of fuel. During high fuel demand (high speeds) the fuel filter has to be airless and filled with fuel so that the fuel pump can suck in as much fuel as it needs during peak demand and not take in any air along the way. If the fuel filter is dirty and clogged, it will starve the fuel pump of fuel causing a Limp mode. If air is in the system and especially in the fuel filter head it will cause a limp mode. First and foremost replace the fuel filter and see what happens. Then maybe install a simple lift pump to keep the fuel filter filled to the brim with fuel continually supplying the high pressure fuel pump during peak demand (the time when the gas pedal is pushed down to the metal). If you haven't already done so, replace the original fuel filter head with the new updated OEM fuel head, the old fuel filter head has been known to cause problems with air leaks and fire. This is just a layman’s explanation and I hope it helps. I am realizing that as time goes by and more issues arise with this little beast of a vehicle that I love, I am being lead to become a second class diesel mechanic through correspondence learning and this board, whether I want to or not. Keep us posted. Racertracer Thats good info, thanks. The filter was replaced about 5K ago but it does still have the stock head. It is fine during hard pulling. I can pull out and hit it hard and it feels very strong and smooth, when I let off of it however and just coast along with my foot barely on the pedal is when I experience the hunching and jumping. Strange, I know... Thanks, Steve

Author:	GreenDieselEngineering [ Sat Nov 20, 2010 11:47 am ]
Post subject:	Re: hesitation at cruising speed
Steve, Try unplugging the MAF sensor on the airbox. This will cause a CEL, but it also shuts off EGR. This may be your light load hesitation issue. If the hesitation disappears, then the EGR system is showing the early signs of clogging internally.

Author:	TennesseeCRD [ Sat Nov 20, 2010 11:41 pm ]
Post subject:	Re: hesitation at cruising speed
GreenDieselEngineering wrote: Steve, Try unplugging the MAF sensor on the airbox. This will cause a CEL, but it also shuts off EGR. This may be your light load hesitation issue. If the hesitation disappears, then the EGR system is showing the early signs of clogging internally. Its been unplugged for about a year now. That was the first thing that I did just after I joined this group and read about it. Is there another maintenance issue that I need to do? I've used the diesel injector cleaner fuel additive so I would think the injectors are clean and it starts right up so I'd say the glow plugs are ok. BTW it has about 75K on it right now.

Author:	GreenDieselEngineering [ Sun Nov 21, 2010 9:53 am ]
Post subject:	Re: hesitation at cruising speed
You state the problem occurs at very light throttle conditions. Any chance it is 'slop' in the driveline (u-joints, CV joints)? With our tune we modify parameters that effect the torsionals at light load and when the pedal is released to reduce the driveline clunk. If it is just a light load issue, chances are it would not be related to fuel. Have you check the codes on the CRD?

Author:	CATCRD [ Sun Nov 21, 2010 12:04 pm ]
Post subject:	Re: hesitation at cruising speed
GreenDieselEngineering wrote: You state the problem occurs at very light throttle conditions. Any chance it is 'slop' in the driveline (u-joints, CV joints)? With our tune we modify parameters that effect the torsionals at light load and when the pedal is released to reduce the driveline clunk. If it is just a light load issue, chances are it would not be related to fuel. Have you check the codes on the CRD? That's why I think it's a resonance in the torque converter. While it's not the typical shudder reported by most, it sound like you're feeling the springs in it bottoming and letting go. Maybe a tube or two of that Dr Tranny instant shudder eliminator from carquest would help. People on LOST have had positive results with it.

Author:	flman [ Sun Nov 21, 2010 4:47 pm ]
Post subject:	Re: hesitation at cruising speed
TennesseeCRD wrote: I may be wrong but it doesn't feel like a trany or tc problem to me although I have been wrong before. It feels more like a fuel problem of some sort. Pulling out from a dead stop it is great but as you get to cruising speed and let off of the pedal some I can feel it start to hump. It is good in pulling and deceleration but just feels funny when no strain at all is on the engine. I wander what the problem was that the GDE tune fixed? Did you get the eco tune? The GDE tune sets the torque parameters in such a way that at cruising speed you wont get the herky jerky feel in the drive line due to the torque converter slipping. If it only does this with you foot totally off the pedal, I would look at other things.

Author:	METCRD [ Fri Oct 14, 2011 12:34 pm ]
Post subject:	Re: hesitation at cruising speed
I experience a little of something that is possibly similar to this when I am on the highway and have the cruise set. Usually if not always it is while going down a slight grade. I believe what is happening on mine is the jeep is traveling at such a speed where any applied throttle will push me over the "limit" set by the cruise and then the throttle will be removed. This will continue happening where the computer is telling the jeep: "apply throttle, coast, apply throttle, coast....and so on". At those times I take off the cruise and speed up (with no shaking) and then coast the rest of the way down the grade if possible. The repeated on/off application of the throttle in addition to having the TC locked up I believe gives me this shaking feeling. Not sure if this is similar to what you are experiencing, but I thought I should share my experience.

Author:	Patrick Henry [ Sat Oct 15, 2011 11:23 pm ]
Post subject:	Re: hesitation at cruising speed
My CRD has been doing this same shudder at cruising/light throttle conditions so I broke out a clear bottle, clear tygon tubing and pumped-bled the fuel filter head a good pint or so. Took quite a few pump strokes to get bubble free. So far shudder free in the driving thereafter.

Page 1 of 1	All times are UTC - 5 hours [ DST ]
Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group http://www.phpbb.com/

Author:	dc3655 [ Thu Oct 13, 2011 11:50 pm ]
Post subject:	Re: hesitation at cruising speed
To the OP, I hope that you figured out the problem with your hesitation at cruising speeds. I just developed the same thing this weekend and I took it to a local tranny shop and they just scratched their head. I figure that it is either air in the fuel or the TC giving up the ghost. I did just change my fuel filter last week, but it ran fine after pumping the head. Any help would be greatly appreciated.

Author:	06CRD [ Fri Oct 14, 2011 2:26 pm ]
Post subject:	hesitation at cruising speed
I have the exact sane problem. I don't really think to much of it. If it starts doing it, I floor it just long enough for it to drop gears and rev up, then problem goes away.

Author:	dc3655 [ Sun Oct 16, 2011 5:18 am ]
Post subject:	Re: hesitation at cruising speed
dc3655 wrote: To the OP, I hope that you figured out the problem with your hesitation at cruising speeds. I just developed the same thing this weekend and I took it to a local tranny shop and they just scratched their head. I figure that it is either air in the fuel or the TC giving up the ghost. I did just change my fuel filter last week, but it ran fine after pumping the head. Any help would be greatly appreciated. For a follow-up, I did pump and prime my fuel pump to get any air bubbles out of the line, but the surging/hesitation was still there. So I unplugged my MAF and the problem has gone away completely. Now of course, I have a CEL now, but it drives very good. The downside is that means (from reading other people's posts) that my EGR is clogged up and so now I need an SEGR kit. I'm starting to realize that if it's not one thing, it's another with this motor.