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Ycheck
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72 Posts
Discussion Starter #1
I have a 2007 GT. Bought used with 50k miles. 2 weeks ago the battery voltage gauge started to drop out... Figured it was the alternator. Took it to a ford dealership to get the alternator replaced. They replaced the alternator and now 2 weeks later the car doesnt seem to be running properly. When I come to a stop the tach drops down to 500 then back to around 900 then back to around 600 then back to 800 and will level off at around 700..

Could this be from the dealership installing a lower amprage alternator?

Any feedback is much appreciated.

Thanks MM.
 

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Premium Member
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33,198 Posts
moved to the correct section
 

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Give it a couple of weeks before you start to trip on it. They unhook your battery to swap the alternator. Once you do that for any length of time you lose your KAM data. Your car kinda has to relearn it's idle settings. There is a process to help this along but I just let it sort itself out and it usuall takes a couple of weeks.
 

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Noob
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You could let it idle for 5 minutes, run the a/c full blast for 5 minutes, then shut off the a/c and let it idle for another 5 minutes to relearn the idle. But it is better to just let it learn itself as stated above^
 

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Ycheck
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Discussion Starter #5
Sorry about that BWAL.. still getting use to this forum scene... I will try to do better next time.
 

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Ycheck
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Discussion Starter #7
I will give it a few more weeks. It has been 2 weeks since it was replaced and is still acting that way. How long does it typically take?
 

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Clean throttle body? Could be that causing it to idle weird. I installed a new high output alternator 2 months ago and there was no idle issues with mine after the install at all.
 

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Ycheck
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Discussion Starter #9
Not sure what it is... thinking about taking it back to Ford and asking them to make it right... I am going to try the let it idle for 5 min, turn the a/c full blast for 5 min, idle again for 5 min and see if that works...
 

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Well, if it's been a couple of weeks I would start looking at other causes. Just funny how it started when you swapped alternators. Clean TB and MAF. Could also be a bad TPS or a small vacuum leak. Double check all our hoses and also check all your intake hoses and couplers, especially on the underside of the TB. Many times the coupler can slip off or it not be put all the way back on when it is removed (which they did at Ford to swap the alternator). Then report back and we'll try and figure it out. Do you have any engine mods or a tune?
 

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Ycheck
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72 Posts
Discussion Starter #11
It does have magnaflo cat backs and a shaker scoop. I called ford and the tech said DO NOT clean the TB as it has a teflon coating and will cause it to stick and a new TB is around $600. As far as the KAM (keep alive memory) he said it will not erase in just a 4-8 hour time frame with no battery. They have done engine swaps that had the battery disconnected for a few weeks and it didnt erase the KAM data. He recommended disconnecting the battery again for 15 minutes and drive it for 40-50 miles mixing city and highway. I dont understand why he would say to do that if by disconnecting for 6 hours wouldn't have erased the KAM data what is that going to do... Not sure if the car was tuned for the cat backs and the tech said they wouldn't have touched the tune if it was even tuned... I will look at the hoses as that sounds the most logical at this point. I appreciate your feed back on this 07Boss. I will let you know if I find anyting with the hoses.
 

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Maybe the idle stuff is not part of the Keep Alive Memory, but either way it should have reset the idle charateristics by now. I would look at something mechanical.
 

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Ycheck
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Discussion Starter #13
Clean throttle body? Could be that causing it to idle weird. I installed a new high output alternator 2 months ago and there was no idle issues with mine after the install at all.
You disconnected the battery? If so how long was it disconnected?
 

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Ycheck
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Discussion Starter #14
Took the shaker off this past weekend to figure out what the deal was with the idle... Found the TB filthy dirty. Cleaned TB and MAF and now the car is idleing like it was brand new! hope that was all that was wrong with it.
 

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Took the shaker off this past weekend to figure out what the deal was with the idle... Found the TB filthy dirty. Cleaned TB and MAF and now the car is idleing like it was brand new! hope that was all that was wrong with it.
You should call the tech back and tell him you fixed it cause the tb was dirty.
 

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The Despised Vert
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also check all of your ground connections.. easy thing to have a loose bolt causing that type of problem..
 
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