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Unread 09-24-2013, 09:54 AM   #1
mobilehomer
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Join Date: Feb 2013
Location: White House, TN
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97 4.0 low power when towing

I have a 1997 4.0 190,000 miles. New 'puter from advance, generic programming. When I tow my Tracker pro team 185, about 2000 lbs, it seems to not have as much power as it should have. Could it be that I need to go to a dealer to have the programming updated?

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Unread 09-24-2013, 10:43 AM   #2
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
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You can check to see if your new pcm has CA emissions with a scanner. That might do it. New plugs and a general tune up may help.....or maybe your cat is clogged.. New o2 sensors might help too. ( use ONLY NTK brand or you'll be sorry !)

Which rear end gear ratio do you have ? I have the 3.73 and although it tows my 17 foot Skeeter just fine....it isnt going to win any uphill races while towing it.

I hope you have a tranny cooler on it if you are towing.
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Unread 09-24-2013, 10:47 AM   #3
zander21510
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1995 ZJ 
 
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Have you towed before? The 4.0 doesn't feel like it has any power pulling anything anyways, I towed probably a 1000lb trailer or less from Uhaul, and it was struggling.
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1995 Jeep Grand Cherokee;
207,000 miles (2/6/14)

206k: 1/6/14;
205k: 12/21/13; 204k: 11/22/13; 203k: 10/8/13; 202k: 8/29/13; 201k: 7/15/13; 200k: 6/8/13; 199k: 5/10/13; 198k: 3/17/13; 197k: 2/22/13;
196k: 12/20/12; 195k: 10/26/12; 194k: 8/17/12; 193k: 5/29/12; 192k: 3/16/12; 191k: 2/18/12;
190k: 12/31/11

Current mods: 703 injectors(my howto), intake modification, 99+ intake manifold (my howto), Magnaflow hi-flow cat from Kolak & Cherry Bomb glasspack.
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Unread 09-24-2013, 10:59 AM   #4
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
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Quote:
Originally Posted by zander21510 View Post
Have you towed before? The 4.0 doesn't feel like it has any power pulling anything anyways, I towed probably a 1000lb trailer or less from Uhaul, and it was struggling.
Yup...this is true. Punch in your OD button on the dash too. Just get a running start on hills. I "hit" an intracoastal canal bridge last month in south Louisiana while towing my boat at 75 mph so I could make it over the top. Air off, OD switch pushed in and hauling azz...
that's WITH the 3.73.
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."
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Unread 09-24-2013, 11:01 AM   #5
mobilehomer
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Thanks, guys. I reckon it's just something I will have to put up with. Did not try OD switch.
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Unread 09-24-2013, 11:20 AM   #6
Josef86
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1996 ZJ 
 
Join Date: Dec 2011
Location: Houston, TX
Posts: 268
My old worn out 4wd 4.0L XJ towed better than my uncles properly maintained 2wd 4.0l ZJ.

I've towed our Glastron GT225 which is 22 ft, and 4400lbs w/trailer. My concern on that trip was brakes(which did well) and wheelbase(which was scary as **** even on stock set up). But I've got the 5.2l and 3.73s, so getting it going isn't an issue. Its the stopping that will always concern me.

Once I get out of Houston...I don't have to stress the brakes.
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Unread 09-24-2013, 11:54 AM   #7
zander21510
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1995 ZJ 
 
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Location: Dallas, TX
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Quote:
Originally Posted by Josef86 View Post
My old worn out 4wd 4.0L XJ towed better than my uncles properly maintained 2wd 4.0l ZJ.

I've towed our Glastron GT225 which is 22 ft, and 4400lbs w/trailer. My concern on that trip was brakes(which did well) and wheelbase(which was scary as **** even on stock set up). But I've got the 5.2l and 3.73s, so getting it going isn't an issue. Its the stopping that will always concern me.

Once I get out of Houston...I don't have to stress the brakes.
Probably because the 4.0 can barely move the ZJ's heavy *** by itself anyway lol.
__________________
1995 Jeep Grand Cherokee;
207,000 miles (2/6/14)

206k: 1/6/14;
205k: 12/21/13; 204k: 11/22/13; 203k: 10/8/13; 202k: 8/29/13; 201k: 7/15/13; 200k: 6/8/13; 199k: 5/10/13; 198k: 3/17/13; 197k: 2/22/13;
196k: 12/20/12; 195k: 10/26/12; 194k: 8/17/12; 193k: 5/29/12; 192k: 3/16/12; 191k: 2/18/12;
190k: 12/31/11

Current mods: 703 injectors(my howto), intake modification, 99+ intake manifold (my howto), Magnaflow hi-flow cat from Kolak & Cherry Bomb glasspack.
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Unread 09-24-2013, 03:18 PM   #8
Oldfrog
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1997 ZJ 
 
Join Date: Feb 2008
Location: Louisiana/Texas
Posts: 2,936
Yeah, but I bet there are more 4.0s around with 250K on them than 5.2s.
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Words of wisdom, Posted by Zeejay:
"..it's not air, it is the opposite of air... suckage so to speak."
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