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Discussion Starter #1
Hi, all- hope you can give me some help with this problem which my Chrysler dealer has been unable to fathom. I have a 2007 Magnum SXT which I dealy love - I tend to become emotionally attached to my cars - and the car has been a model of reliabililty until this past spring when, all of a sudden, it started to rev up while it's idling. What happens is I've stopped in traffic, light, etc. foot on brake (nowhere near the accelerator) when all of a suddent the car starts running rough (have a high-output six), starts to cut out but then revs up to over 2 rpms. Of course, it never happens while the dealer has the car. The dealer has run all sorts of tests and even reprogrammed the transmission, but it hasn't helped. It doesn't happen all the time- randomly -sometimes two or three times in a day, sometimes once a week. Last week, though, it behaved a bit differently. It started cutting out, and then revved up, but at the same time, my headlights brightened. This was a new thing - never happened like that before. I have an extended warranty on the car which is due to run out next year - hope someone can come up with a solution before my warranty runs out. Any suggestions would be greatly appreciated.
 

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I suspect the problem may be a vacuum leak. That would explain both the roughness and the increase in RPMs. But where? I have no clue to narrow it down.
 

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Agreed! Vacuum hoses should be replaced one at a time until the issue goes away. Common problem with most cars, and it's usually in the evap circuit. If that's it, replace them all.
 

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This car has the ETC (electronic throttle control) and while they stay troublefree for the most part, they can go bad. The dealer scan tool can reset and calibrate the accelerator pedal sensors, run tests and get fault codes. Does the 'ck eng' or 'lightning bolt' warning lights ever come on? Have there ever been fault codes found?
Does this happen only warm or cold or when the A/C or windshield defroster is on? An improved MAP sensor was released with a raised plastic 'H' rib on the part itself (part # 5033310AC).
Does it seem dependent on how much gas is in the tank or act up right after a fuel fill-up?
Vacuum leaks will tend to cause a fast idle and this would need to be diagnosed while it is acting up if no clues are being left behind. If it isn't acting up, you may find nothing.
The dealer also has a Co-pilot tool that can record data while driving. Have them program it and install it and you just press the button when it acts up so they can get a read-out of what the PCM was seeing at the time of the failure. The Co-pilot can hold up to 3 - 90 second recordings of what was going on with the engine sensors/actuators.
 

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Discussion Starter #5
Thank you all so much for your help. Vacuum problem it was - it seems the PVC valve was blocked. The dealer had to call Chrysler - wouldn't take my word for it when I suggested they check the hoses - but it looks like the problem is taken care of - it took the dealer three visits to finally call - no codes came up and naturally, the Magnum behaved beautifully when they drove it, but just from the way it sounds now, I think the problem has been solved - we will see.

In the meantime - what would cause that valve to block up? Anyone have any ideas?
 

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It's normal for it to clog over time. That's why it's a regular replacement item in tuneups.
 

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Discussion Starter #7
Thanks for the info re the PVC - haven't had a tuneup yet on the Mag because it's only got 21,000 miles on it since I bought it new in 2007 - and it's always passed our state inspections. Probably clogged up just because it hasn't been driven on the highway very much but that's about to change . I'm going to be doing a lot of highway driving this summer. Thanks to all of you for your help.
 
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