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Unread 08-06-2011, 10:09 AM   #1
will_982
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1994 YJ Wrangler 
 
Join Date: Oct 2007
Location: central pa
Posts: 241
4.0 temperamental hesitation

I have a 94 4.0l that has been giving me some issues. It started with a day long trail ride, everything was great till I got back on the main roads and at about 3000 rpm the Jeep acted like I threw an anchor out the back. I could barely make it up hills and the I was getting back fires from the raw gas in the tail pipe. I ended up getting some premium gas at the next station and everything cleared up and ran great. I figured maybe I got some bad gas so I replaced the fuel filter and went on. Now it seems like it is back but it only comes after about a half hour of diving it is not as severe as the first time.

Any ideas what I should look at, seems I wouldn't get back fires if it were a fuel problem and my cap, rotor and plugs look clean.

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Unread 08-06-2011, 10:25 AM   #2
bigbossd1030
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1995 YJ Wrangler 
 
Join Date: Feb 2010
Location: Edmonton, AB, Alberta
Posts: 2,515
After driving for 30 mins, is it a slight jerk, kinda a loss of power, then it fluctuates?
I would say TPS, I just did mine last month, same problem, Its actually kinda funny, I did the premium thing too and it made it better, Hmm.
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Unread 08-06-2011, 10:30 AM   #3
will_982
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Location: central pa
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Yes, fluctuates allot almost like my passenger has a brake pedal and is just trying to p*** me off by hitting it.
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Unread 08-06-2011, 10:33 AM   #4
bigbossd1030
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1995 YJ Wrangler 
 
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Yeah its your TPS.
First it might be a bad connection on your TPS, so remove the plug and clean it out, then use some dielectric grease on it. If that doesnt help, you need a new one.
It is on the side of your intake, Ill see if I can find a picture and post it asap.
Oh and check for codes as well.
Turn key on, off, on, off, on and wait for the CEL to flash.
Then use this page to determine codes.
http://www.jeepforum.com/forum/f12/c...t-how-1230753/
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[COLOR="Blue"]OFFICIAL JEEPER[/COLOR]
[COLOR="Red"]Any Jeepers in Edmonton, AB
I am on channel 33.[/COLOR]
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Unread 08-06-2011, 10:37 AM   #5
bigbossd1030
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1995 YJ Wrangler 
 
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Location: Edmonton, AB, Alberta
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Ok here are a few pics, it is on the side of the intake closer to the firewall.
images123.jpg   images1234.jpg  
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I am on channel 33.[/COLOR]
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Unread 08-06-2011, 10:45 AM   #6
will_982
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1994 YJ Wrangler 
 
Join Date: Oct 2007
Location: central pa
Posts: 241
Alright I will swap that out, nice cheap fix too. I did swap this out about 2 years ago when I was having different problems. Give it a try thanks
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Unread 09-02-2011, 09:32 PM   #7
will_982
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Location: central pa
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Well, it reared it's ugly head again. I swapped the tps and it does run smoother now but it still gets a hesitation. I went on a trail ride, drove about 45 min on the highway ran perfect, then after driving for about 2 hours at an idle or close to it on the trails I got back on highway at 70 mph and after about 20 min it started with the hesitation. I am still running the premium gas in it (liked the gas mileage I got with it). Any other things I should look at? I don't understand why it worked so good on the ride out then I let it idle me thru the trails then when I needed the high rpm for speed again it let me down.
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Unread 09-06-2011, 10:06 AM   #8
bigbossd1030
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Location: Edmonton, AB, Alberta
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if the tps fixed it then it came back then I'm still thinking its the tps, clean the connection and use dielectric grease on it, and try it again... any codes?
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Unread 09-06-2011, 02:44 PM   #9
will_982
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1994 YJ Wrangler 
 
Join Date: Oct 2007
Location: central pa
Posts: 241
I'm not sure if the tps really fixed it, I think it runs a little better because I used to get a small back fire out the exhaust, (kind of like a fart). When I would rev up then remove my foot from gas and start to shift I would hear a poof out the exhaust. I have not heard this since the new tps. All my connections are clean into tps and no funky codes coming up.

I should mention this is not at a daily driver, I just beat on it on the weekends when I get some spare time so since me first post about this problem I maybe put 200 miles on it and that was just on that 1 road trip.

The whole thing just seems like it starts to act up when it sits at an idle for a long period of time then has to do some high revs.
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