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Old 05-02-2008, 06:37 PM   #1
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Rough Running 4.0 Sahara

My 4.0 Sahara is running really rough, it doesnt do it all the time but often while your out driving it, the revs will jump up and down like crazy and then the engine will cut out, it does it in all gears??
We took it into our local jeep dealers and theyve been working on it for 2 weeks now! They cant find the fault, they've replaced the complete electrics, the Idle Air Comtrol Motor, all service parts?? We picked it up tonight thinking it was fixed but we only got 10 miles from the dealer when it did it again on the ring road doing about 50mpht!! We took it back but the mechanic says hes going to leave as hes never had to work on such an annoying vehicle
it sound liek an air leak to me but they cant find one

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Old 05-02-2008, 07:05 PM   #2
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You mean vacuum? Could be. Check all the hoses and see if you have a leak.

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Old 05-02-2008, 07:28 PM   #3
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Was the Throttle Position Sensor replaced?
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Old 05-02-2008, 11:31 PM   #4
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Throttle Position Sensor or Upstream O2 Sensor are my guesses. Could certainly be a vacuum leak.

Dealerships tend to jump to the most expensive conclusion for some reason. Eliminate the simple things first.

Try a new battery?
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Rotting piece of junk with some bling in the rear axle.
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Old 05-03-2008, 01:13 AM   #5
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Old 05-03-2008, 02:41 AM   #6
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try the throttle position sensor
make sure the throttle body and the idle position sensor is clean
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Old 05-03-2008, 02:44 AM   #7
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Quote:
Originally Posted by mr4x4 View Post
try the throttle position sensor
make sure the throttle body and the idle position sensor is clean
idle air control valve
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Old 05-03-2008, 09:11 AM   #8
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thanks guys, the delaer isnt charging anything for the parts or the labour as theyve had it so long, theyre brilliant!!
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Old 05-03-2008, 06:20 PM   #9
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Originally Posted by fleet View Post
thanks guys, the delaer isnt charging anything for the parts or the labour as theyve had it so long, theyre brilliant!!
the dealer is brilliant. that opinion will change after you see them a few more times
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Old 05-03-2008, 11:03 PM   #10
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I have an exhaust leak, drop dead sure, and the dealer told me its just the way the 2.5 sounds...bahahaha. Anywho they had to do 8 hours of labor prior because of a broken exhaust manifold stud...makes the header I'll be getting much easier to install. The same dealership told my friend that a small dent in his oil pan caused his rear main seal leak on his 06 rubi. Maybe cause his warranty runs out in a few thousand miles? haha. Only had a 30 day warranty on mine, and that's over. I'm sorta relieved that I'll have to do everything myself now.

Hope you get your Jeep back running real well. Milk the stealership for all they're worth. They deserve it.
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Rotting piece of junk with some bling in the rear axle.
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Old 05-11-2008, 04:48 PM   #11
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Hi Fleet
I'm also here in the UK and have been battling with similar problems. Turned out that the throttle position sensor was the fault. I had fitted a new one but not used a genuine part and the replacement was crap! Also took it to the dealer here in oxford and tey could not fault it or fix it. In a last ditch attempt to fix it - bought a genuine TPS fitted it and its running great! Give me a call on 01235-832100 bus hours, and I am sure I can put you in touch with a reputable jeep specialist garage.
Cheers
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Old 05-22-2008, 02:45 PM   #12
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Thanks for the replies, only just seen them.
We've replaced everything that you all said and its still doing it.
Its only does it when its cold and ive found out if you switch the engine on and off it clears. Could it be the fuel pump?
Thanks
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Old 05-22-2008, 09:43 PM   #13
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Have you got a way to run a fuel pressure test to see if it is the fuel pump?I would try the least expensive first with the fuel filter providing it's not on top of the fuel pump like the Dakota trucks.If it is accessible I would change it first and while at it run a fuel pressure test on the line at the filter I think the fuel pressure for the 4.0 should be around 39-42lb I may be wrong on that so if some one wants to chime please do.

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