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Unread 05-26-2009, 05:02 PM   #1
JFiorentino
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2004 TJ Wrangler 
 
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2007 GC Surging felt at slow steady speeds

Hello,

My 2007 GC has done this since I bought it used last year. I've taken it the dealership several times, but they claim to find nothing. My warranty is about to end, so I thought I'd give the forum a shot.

When I'm driving in town, Maybe 35 to 45 miles per hour, going steady with my foot very lightly on the gas, just enough to maintain speed, not speed up, I get a surging sensation that I can feel in the seat of my pants. My GF had her purse on the floor and we could hear her keys jingle at the same rate of the surge.

It's not a super noticable thing, but I can feel it being I drive it daily. The Jeep has a 4.7L V8, it has full time 4x4. On my last trip, the dealer changed my TPS (mainly to shut me up) but this didn't help any. I still get the light surging sensation. If I give it any more gas, the engine downshifts and RPM's race up past 2,000 and the surging goes away.

I do have a K&N Intake system on the Jeep. Could this be the cause??? I've run several different fuel engine cleaners like Lucas and seafoam through the tank, but noticed no change.

I changed the spark plugs, which made no difference at all.... It almost feels like the Jeep's RPM's are too low for the speed. As I approach inclines, the engine feels like it's losing power, then it downshifts and everything is fine.

Any ideas?????

John

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Unread 05-26-2009, 08:01 PM   #2
TJJP77
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Try "tow/haul" mode and see if that makes it go away. What I suspect is happening is the torque converter clutch slipping a bit as you lug the engine at the low end of it's engagement speed. Enagaging "tow/haul" allows the torque converter clutch to slip more just like cars did when they had non-lockup converters, which should mask the sensation.

edit: I just remembered there is a TSB for this: 18-004-09 Rev. A. If you do what I said above and that "cures" it, then the TSB should help since it will change the lockup speed. Be forewarned though, changing the lockup speed can reduce fuel economy depending on your drive cycle.
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Unread 09-25-2010, 10:24 PM   #3
rickwil61
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I have an '07 Laredo 4x4 QT1 with a 3.7L that does the same thing. I bought it used about 3 weeks ago and it has 28K mi on it. There is what feels like a slight miss or hesitation that happens at a high rate. You do feel it in the seat of the pants but it is hard to point out to anybody. It's like there is something that cuts on and off fast enough that the vehcle moves forward without any major lurching. I don't see any fluctuation in the tachometer and don't notice any miss in the engine when idling. I had an emission test done, to get license, and it passed with flying colors so there doesn't seem to be anything major wrong with the tune. The miss seems to smooth out when the vehicle is under a pull. Should I start looking at the engine or the drive train? What could be causing this? Any experiences or suggestions would be greatly appreciated. Thanks.
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Unread 09-26-2010, 06:11 PM   #4
jmolli
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I have a 2005 GC Laredo that I bought new. It developed a similar lurching/surging problem at around 30K miles. It was particularly noticable at slow, constant speeds while going up a slight incline. I immediately suspected a problem with the tourque converter slipping. After 4 trips to the dealer where they claimed they couldn't feel it and it didn't show any slippage on there diagnostic computer, I finally lost my mind and made a big scene. When they finally looked at the fluid, it looked a little burnt. They dropped the pan and everything inside the trans was coated with burnt fluid. They ended up dropping the trans and replacing the torque converter. Problem solved.
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Unread 09-27-2010, 12:27 AM   #5
rickwil61
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Thanks for your reply. Perhaps I'll take it in for a transmission service and see if they find anything similar.
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Unread 09-27-2010, 09:55 AM   #6
90grandoneer
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Sounds exactly like an EGR valve going out. How many miles on it? See my recent post on the EGR. I think it would apply to all the Chrysler engines that have an electronically controlled EGR system.

http://www.jeepforum.com/forum/f67/e...tions-1107386/
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Unread 09-27-2010, 12:44 PM   #7
rickwil61
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I've got 28K on it now. I don't notice any problems with rough idling or poor gas mileage. I drove about 250 miles the other day and was getting 21.75 MPG. Even though it doesn't have those symptoms, do you still think the EGR could be causing the surging?
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Unread 09-27-2010, 02:50 PM   #8
90grandoneer
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My guess is, no, because most people that have had this issue (at least on the 5.7's) have a definite loss of performance and fuel economy, and the surging is very noticeable at light throttle. Is yours doing it when the engine is cold. The EGR system doesnt' start working until the engine operating temperature is at ~120 degrees or above. One thing you may want to do is check if there are any outstanding Technical Service Bulletins (TSB) that apply to your vehicle. You can check here (http://www.wkjeeps.com/wk_tsb.htm) to see if there are any that sound like your problem.
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Unread 09-27-2010, 03:04 PM   #9
rickwil61
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I still feel the surging even when the engine is warm. I just feels like a subtle pulsating in the drive train because I don't see any fluctuation in the tach. I tried the link you posted but it looks like the site is down right now. I'll give it a try later.

BTW will a dealer charge for work on a TSB if the vehicle is out of warranty?
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Unread 09-27-2010, 05:05 PM   #10
90grandoneer
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The web site is back up now. Yes, the dealer will likely charge you for TSB's if you're out of warranty.
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Unread 09-28-2010, 12:24 AM   #11
rickwil61
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OK. I spoke to a couple of dealerships today and one guy said that it sounded like it could be the torque converter locking and unlocking. The other guy said that they would need to put a computer on it and take a drive to see what's happening. He said there may be a flash that can fix it. I found a TCB for a hesitation condition on the link that you sent but it was foir a 4.7 L not a 3.7 L. Looks like I'll probably need to go to a dealership with this one. Thanks for your help.
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Unread 10-11-2010, 12:33 PM   #12
Jdmick
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My 3.7 has been doing this same thing. I took it into the dealer over the weekend to see if they could try a reflash to try to fix it. When they checked it out they found a code that said that the tranny fluid temp has exceeded 250 degrees, and the fluid looked black and burned. I wasn’t sure if the two issues were related until reading this thread. But my first thought was to change the fluid, but I’m concerned that it might make it worse. Do you guys think I should try changing the fluid, or just let the dealer tear into it?
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Unread 10-11-2010, 07:35 PM   #13
90grandoneer
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Have you looked, or is this just the dealer talking? What color is the fluid? Does it smell burned? If it is indeed black and/or smells burned, I would definitely pull the pan and look for crap in the pan, change the fluid and filters. If there is debris in the pan, you most certainly have a problem and continuing to drive it will only make it worse.....cost more in the long run. Was it used for towing heavy loads, run low on fluid, or ???

I am not sure why so many people are having trouble with the NAG1 trans. behind the 3.7 engines. I have one in my Hemi LX and the SRT WK's have it. Mine works great, always has, and I've not heard any of the SRT folks complaining about it. Makes me wonder if they put different components in the 3.7 ones???
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Unread 10-12-2010, 06:40 AM   #14
Jdmick
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Because it doesn't have dipstick, I have no way to verify it w/out going to another dealer. But when I pulled the plug where the dipstick would be, it doesn't smell burned to me. We bought it a little over a year ago w/ 35k miles, and put 10k miles on it since. Within a month of buying it, the SES light came on. I brought it to the Carmax where I bought it, and they said it was a mis-communication code that was normal in these Jeep's. It doesn't have a tow package, and because it was used, I don't know how it was run before.

I would just go and pull the pan if it wasn't my wife's car, and now she wants to just cut our losses and trade it in. But I would hate to pass this issue on to someone else if the dealer doesn't fix, but would also hate to put a ton of money into it if we are just going to trade it.
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Unread 10-12-2010, 10:02 AM   #15
90grandoneer
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Yes, I forgot. The NAG1 doesn't have a dipstick. In the almost 6 years I've had my LX, I've never checked the fluid. This is because I figure if I don't have an unidentified puddle on the floor or a wet transmission pan, I don't have a leak. It is getting close to my fluid/filter change schedule, so I am sure I'll be looking at in the next year or so. It's not driven near as much as my WK. When I do the next change on either, I am going to install drain plugs. I've already got them on hand, ready to go.

You can make a "fluid sampler" out of a piece of welding rod, an old metal hanger, or ??? Just make it long enough (you can measure the length of the dipstick tube) to get to the bottom of the pan. I think I'd also try to flatten it out a little and perhaps file some notches in it to sort of grab the fluid when dipped. Then you can check it for yourself. I have found over the years that there aren't too many dealers I'd rely on for accurate and truthful information.

On my LX, when I change the fluid/filters, in addition to the drain plug, I am going to make my own dipstick. I have the DashHawk Info. Display which I have set to read trans. temp. on one screen. I can then take readings at different temps. and mark my stick accordingly. The shop manual will also show me the correct readings for the various temps.
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