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Unread 03-04-2010, 10:29 AM   #1
HPJeep
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2003 TJ Wrangler 
 
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momentary hesitation around 2000 rpms

I have a 2003 with the 4.0 and manual tranny. Owned it since new and just turned 60k miles on it yesterday. I get infrequent hesitation or stumbling while driving at highway speeds. Usually occurs around 2000 rpms and only lasts for a split second. Does not do this at idle at all, only under load. It does not do it all of the time but just once or twice a week. Seems to occur more frequently compared to a year ago. Everything on the engine is bone stock except for K&N air filter. Heck I'm still on the original battery!

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Unread 03-04-2010, 01:48 PM   #2
GeneralTJWillys
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Bad gas? Maybe your fuel filter's getting plugged? Can't be sure, but these are places to start.

I've got an '05 TJ with the 4.0 and 6 spd manual. It now has 69k miles and, while I've not experienced this yet, I'll be watching out for it.

I do know that mine will hesitate, but not stumble, but I believe this to be a product of the factory tuning. It almost acts like a turbo, waiting to spool into the power range. It's odd that they would program something like this in, but I can only imagine that it's there to help when off roading, when you want smoother application of power without a heavy surge that may cause lost traction in certain crawling situations.

Since I do some rock crawling, I've not done anything about this. It's already tougher to rock crawl with a stick than an auto, so I think it helps that it's held back a bit at those times. JMHO though.
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Unread 03-04-2010, 04:33 PM   #3
HPJeep
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Thanks for the reply GeneralTJWillys. I don't think its the gas because I buy it at many different gas stations. Doubt its the fuel filter since it only does it around the 2000 rpm range and not all of the time. However if others had the same stumbling/hesitation issue due to the filter than I will change it out. Any other possible ideas?
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Unread 03-04-2010, 11:55 PM   #4
GeneralTJWillys
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Really didn't think it would've been the filter, but it was a place to start. It could be removed and easily checked by blowing thru it, eliminating it as a possibility.

I'd say possibly the TPS, but from the way you describe it, it does not matter at what position the throttle is.

After thinking for a while, the only thing I can think that possibly makes sense is a problem with timing and/or ignition. Am I correct in assuming that the 2003 models had gone to coil on plug ignition, or do you still have cap/rotor with a separate, single coil?

If you have a separate coil, I'd say try to swap it out with a known good one. If it's coil on plug, well, the coil check will be more difficult. You'd need to swap the whole coil "rail".

Right now, that's all I got, but I'll be giving this more thought and consulting with a friend of mine to see if he has any ideas.

As a precaution, check for any loose or broken vacuum lines, just to eliminate them as a possible culprit.

Good luck!
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Unread 03-05-2010, 05:01 PM   #5
HPJeep
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Yeah I'm leaning towards it being the TPS but have no idea if this can be fixed in my garage or if I need to take it to a shop. Any write ups on changing the TPS and how much it may run? You are correct that 2003+ have no distributors but has coil on plug ignition. I'm old school so I have no idea about how to test this type of system. Any other ideas on my stumbling/hesitation issues? Thanks yall.
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Unread 03-06-2010, 12:38 AM   #6
GeneralTJWillys
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TPS is a fairly simple thing to do. You can do this in 5-10 minutes in your driveway. Unplug it then remove 2 or 3 screws and it's out. But, like I was saying, it's likely not the TPS because you say it's more a product of RPM than it is throttle position. If you know someone with a similar jeep, ask if you can swap the TPS to see if the problem shows on his and goes away on yours. Cheaper than buying a new TPS that you won't be able to take back (electrical item), if that's not it.

For the coil packs, I'd definitely do that. Swap with a friend first. WAAAY too expensive to be guessing there.

As before, if I find any more info, I'll let you know.
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Unread 10-30-2010, 03:35 PM   #7
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I've been having the same problem as the OP. Engine will stumble/hesitate/misfire only at 2000 rpm, and more noticable under load. I've replaced the TPS, cap and rotor, Crank position sensor, IAC, spark plugs, and wires. still happens, and more frequently now. I even tried running premium gas for a couple weeks with injector cleaner, but that didn't do anything except waste my money.
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Unread 10-31-2010, 10:26 PM   #8
GeneralTJWillys
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Even thought this may not be likely......check for vapor lock. When you start having this problem again, shut off the engine and go to the fuel rail's schrader valve. Have a good sized rag ready to block fuel from hitting hot exhaust. Protect your eyes too. Push the schrader valve........ALL you should get is a stream of fuel. If you get ANY air, then there is vapor lock. You can do this check as often as you need, when this happens. You'll just need to turn on the key after each check to re-pressurize the fuel system for the next check, obviously.
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Unread 10-31-2010, 10:39 PM   #9
Addisonjeep1363
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I have 2004 5-speed that had a problem very similiar to this. would be accelerating until about 2000rpm and it would slow and then pick up again quickly. This started around 60k, but i just lived with it. Then around 67k it my engine light came on, then it went off, came on, back and forth. Pulled an oxygen sensor out of the downstream bank 2(most rear catalytic converter coming off of the header) and it was very sooty and dented.

Confused to what caused it, I pulled off the exhaust midsection. Sure enough, the Jeep had blown the guts out of the converter and it was trapped between the header converters and the larger rearward converter. Replaced it free of charge thanks to the government emissions warranty, and know the TJ runs flawlessly. Very noticeable power increase at lower rpm's I might add.
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Unread 12-29-2014, 03:30 PM   #10
TJMerlin
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I've had the same sounding issue (rpm related) since buying my Jeep TJ brand new in 1996. 226,000 miles later I still have the issue. I never got any mechanic to acknowledge or solve this mysterious "hesitation/pause/hiccup" at around the 2000 rpm mark. And it hasn't developed into anything else. It still puzzles me and I'd love to hear what it could be.
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Unread 12-29-2014, 06:06 PM   #11
JeeperLink
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Since the thread got bumped anyway, I will chime in and say that my 01 TJ 2.5L has the same "burp" at ~2000 RPM. After a new cap, rotor, wires and plugs, I still have the burp. I have a cracked exhaust manifold, so I will be putting in a new exhaust, so that means new O2 sensors and see if that does anything..
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Unread 01-02-2015, 09:15 AM   #12
GoGetEm1994
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Happy New Years everyone!!

I am having the same issue with my Jeep, are any of you getting code P0171?

I have a 2001 2.5l. After driving around for 15 miles,the jeep jolts when I accelerate in all gears at 2k rpm. When it is idle and even when driving there is a heavy gas smell. CEL code P0171, I replaced spark plugs, wires, distributor cap and rotor, oil change, TPS sensor, Map sensor, 02 upstream sensor, exhaust manifold, catalytic converter, and muffler. Still no luck. This issue only appears when the engine gets hot, usually after 15 miles of riding.

Would appreciate some feedback of what you think is the issue!
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Unread 01-28-2015, 02:44 PM   #13
TJMerlin
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Well, I did a complete tune up and also cleaned my K&N air filter for the first time in quite a while. After a 1000 miles, so far so good. No hiccup or burp at 2K rpm. I will just keep a watch to see if/when it returns.
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Unread 01-28-2015, 05:19 PM   #14
Jaminjer
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same problem, at about 1900 rpm slight hestitaion under light acceleration
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Unread 01-28-2015, 05:54 PM   #15
JBTJ
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Quote:
Originally Posted by TJMerlin View Post
Well, I did a complete tune up and also cleaned my K&N air filter for the first time in quite a while. After a 1000 miles, so far so good. No hiccup or burp at 2K rpm. I will just keep a watch to see if/when it returns.
That sure isn't helping. Probably sucked in some dirt in the TB.
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