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Old 03-03-2009, 10:15 PM   #1
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mystery engine problem

ok im going to try and explain what is happening in detail...hopefully someone on here can help...because the dealer ship sure cant ok i have a 2006 jeep wrangler unlimited. when i am driving and reach the speed of 45 mph up to 55 mph something with my acceleration happens. at first it only happened when i was going up hill but now it has progressed to any driving condition except down hill. at 45 mph my RPM is usually around 2100. once i hit 45 the rpm will drop to about 1100 followed by a strange rattling grinding noise. if i am going up hill the speed will slightly drop unless i really press the gas peddel. if i am on flat terrain it will ( most of the time ) hold its speed and VERY slowly increase when i press the peddel. i can press the gas peddel about three inches with NO engine response...i mean the speed will slowly increase but the rpm's are unresponsive. once it is past 55 it will generally cut out and return to normal unless i let off the gas...and then reapply the gas...then it will repeat this problem for a couple of seconds. usually once i get the acceleration to respond it is almost floored. this problem began while i still had my warranty but only occured between 45-50 mph. i took the car in on several different occasions only to have them tell me that they couldnt find anything wrong...i just have a feeling that they didnt really try that hard in the first place. i specifically asked the mechanics to drive it to see exactly what i was talking about, but every time i got the car back there were only like .2 miles added to it. which showed me that the only time they drove the car was to move it in and out of the bay. my warranty has expired now and i am hessitant to take it back to them simply because i feel that they will " magically " find some serious problem with the car. i am desperate to find out an answer to this problem. i have heard of the 2007's engins stalling out occasionally but im not so sure that this would qualify for that. can anyone help?

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Old 03-03-2009, 10:48 PM   #2
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Some of the symptoms sound to me like the catalytic converter is broken loss and causing it to clog and restrict the exhaust flow and part of it could also be rattling around making the noise.Hard to say for sure though without looking and listening to it.

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Old 03-03-2009, 10:49 PM   #3
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Since you complained about the problem recently - before the warranty expired, you are still covered.
The incompetent dealer will give you a song and dance, but a call to the factory rep will clear it up.

Sounds like you have a plugged exhaust. The rattle you hear is a baffle moving around in the cat or muffler.
Take it to a good muffler shop - not a chain store like Midas or Advance - a chain store will screw you big time! Find an independent guy - tell and show him the problem. Ask around shops as who is good and who is not. Most shops send out their exhaust work - they'll know who is good.

They can measure intake manifold vacuum and even do a backpressure test. Cost? Not much if any. Have him write an estimate showing what's bad.

Then take it to a DIFFERENT dealer - the record of your complaint during warranty is in their computer. The rep can intercede if needed, and you can call his office and talk to his boss if he doesn't.
If the dealership didn't enter it in the central computer during warranty, and gave you a receipt so you can prove it, he can lose his franchise!

2006? Remember even if they lied - exhaust and cats are are part of the emissions system, warranted 70,000 miles.
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Old 03-03-2009, 11:19 PM   #4
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man...i wish that was the problem....actually my check engine light came on around 37000 so i took it to auto zone for a free diagnostics (sp) and he told me it was my catalytic converter...so i took it to the dealership...even though my warranty was expired there was a 70000 mile warranty on the converter and they replaced the whole thing....but the intake manifold vacuum and backpressure test sound like a good idea...i will deffinatly give that a shot...and i knew i was still covered simply because i did take it to them several times but i didnt know that they could possibly loose their francise...i have just been waiting for someone to figure out the problem so that i could actually take it back...and thanx for the advice on contacting the factory rep....i was woundering how i was going to go around all that. agan thanx guys for the advice...but since the catalytic converter was replaced do you still think it could be related to that?
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Old 03-03-2009, 11:31 PM   #5
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this is such a hard problem to describe...it really is one of those things that you have to hear or feel...like the engine just completly boggs down and you can feel the rattle but it sound like it is coming from the engine
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Old 03-03-2009, 11:33 PM   #6
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its almost like it switches to fith gear to early...and just looses all throttle response
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Old 03-04-2009, 02:30 AM   #7
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my 02 does that goin through town at about 20-30ish. if i am just cruisin it has some bad vibes and a rattle, but if i give it more gas, or select 2nd it goes away...


i have 90000 on mine, and i just bought it a month ago...
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Old 03-04-2009, 05:13 AM   #8
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Sucks to hear, hope you're able to get it resolved. If worse comes to worse, it could 'spontaneously combust' in your driveway....*ahem*.....what kinda insurance you carrying?
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Old 03-04-2009, 07:16 AM   #9
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It could also be the muffler's plugged - or the pipe's smashed somewhere.

Symptoms of a plugged exhaust - as you accelerate it hits a "ceiling" and doesn't want to go any faster. Happens even going downhill, just at a slightly higher speed.


Vacuum - vacuum gauge on manifold vacuum - drive it - vacuum drops to near nothing at that ceiling. from idle - Snap it - first part of snap vacuum drops fast, then snap it closed, vacuum's very slow to recover, should "bounce" way up on deceleration.

Pressure test - they drill a small hole ahead of the muffler/cat - then hook a pressure gauge to it. At the ceiling it creates lots of pressure. They plug the small hole afterwards with a screw.

Stand behind it while someone revs it - exhaust sounds like a hissing noise.

Temperature - laser type thermometer - before the clog is super hot, after the clog is much cooler. Run the R's up for a minute before testing.

Measure the temps of both pre-cats both in and out, Should be about 500 degrees in, and about 400 out. 700 on 1 and 400 or less on the other indicates a bad ignition coil rail.

Could also be the ignition coil rail - the only real way I know to test it is swap in a known good one. There are all kinds of "tests" some folks use - all snake oil. Myself I've replaced several that supposedly were tested "good" by dealers and "experts?" I keep a spare on hand just for that purpose. Dealership is about $260, Carquest, NAPA etc is about $160. Avoid Autozone and other cheapie stores - unless you want to do it again in a few months. Easy - It's a 5 minute swap.
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Old 03-04-2009, 07:35 AM   #10
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Couple other things:

is this a stick or an auto?
Also is the TPS good? Throttle position sensor.

If auto.. you may have an issue with the TCM. Transmission control mod. On another chrysler product.. ours was make the rpm's jump, or even stall the car. Simple flash of the computer took care of most of it, had to tell the dealer about the TSB for it...lol might be worth looking into if yours is an auto.
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Old 03-07-2009, 11:24 AM   #11
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its an auto...thanks for all the help guys...im taking it to a mechanic this weekend and have him check all of this expeciall the tcm. again thanx
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Old 09-22-2009, 07:44 PM   #12
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Re: Mystery Engine Problem

Hi there, I have an 04 TJ X and I am currently having the same problem as well. Almost the exact same symptoms. My mechanic suggested a tune-up first (I have around 130,000 miles on the jeep with never doing a tune-up). However the same problem still existed. Then, my mechanic took the Jeep to an exaust/muffler specialist who said that 1 of my 4 catalytic converters is clogged. Apparently whenever a vehicle, or at least a TJ, is manufactured in California, the factory installs 4 catlytic converters b/c of emission laws in the state. This all happened today 09/22/2009, so hopefully I will have some good news to post soon. Good luck with your Jeep.
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Old 09-22-2009, 09:03 PM   #13
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I also have the 06 Unlimited and it does the same thing. My solution is free and very simple. What is happening is that when you hit approximately 45-50 the auto tran shifts into overdrive. If you are traveling around town, just push the toggle to turn it off. That is all it takes. I don't know why the O/D is geared so low, but that is what is happening. The sad thing is that the stealerships can't explain this to you. They have to know about it. It is the same thing that would happen if you were driving a MT and started a steep incline in 4th or 5th gear. The rpms are just to low for the gear. Don't get ripped off. They give you the switch for a reason. Remember that everytime you start the engine you have to switch it off for city driving.
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Old 09-22-2009, 11:48 PM   #14
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purely going off the speed that its doing it i think the trans is hitting OD too soon. i would have the TCM reflashed and see if that helps.

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