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Discussion Starter #1
Hi Guys,

I need a little help diagnosing an issue with my v6 convertible.

My car is having an issue after driving that when I put it in part the RPM's just drop out from around 700 to 500 really fast. They then jump right back up to 700 and resume normal idle after a quick studder in the engine. A few times recently however after putting the car in park it has literally just cut the power completely. While this doesn't happen often it has happened on at least 5 occasions in the last 3 months. I brought it to my mechanic and asked about the idle air control valve. I don't even know that this car has one like previous mustangs? Maybe you guys can clarify that one, or is it the MAF? Is my throttle body bad? I had my spark plugs replaced recently. I also went from 2.73 gears to 3.55 gears but the problem existed before and after the gear upgrade and that should not be related. I've read that it could be a vacume leak but the car runs completely normal while driving until I put it in park and again it is a problem that is inconsistent.

There is no check engine light on. My mechanic checked this 2 months ago and said there were no codes at all and he thoroughly tested it for me.

One other thing. I am using a pedal commander for throttle sensitivity. I don't think that should cause a problem but you never know I guess. I'm not sure if I had this problem before I started using that but seems more like a hardware issue to me.

Any help is appreciated. Looking forward to your responses.

Thanks.
 

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Yeah I have been experiencing the same thing lately with my convertible. I had a check engine light come on, said an O2 sensor was bad. Replaced the O2 sensor, seems to idle better now. I doubt the O2 sensor will impact the idle when shifting to park. I have cleaned the MAF and it really didn't make much of a difference. I am assuming it could be a vacuum leak? But haven't found anything yet.

Sent from my SM-G960U using Mustang Evolution mobile app
 

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OP:
Pretty sure you need a tune since you changed the rear end gear ratio. I think the only stock tune that Ford provided for gears higher than the 2.73 was the performance package which had the 3.25 gears. I’m not sure if that has anything to do with your idle issue, but when you go higher than 3.25 gears, you need a tune to compensate for the gear change. I don’t know if you have the stock tune or a custom tune as that wasn’t mentioned in your original post.
 

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I believe he had his Bama 'tunes for life' changed for his 3.55 gears :)


Performance Package v6 Mustangs has 3.31 rear gear ratio :)
 

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I believe he had his Bama 'tunes for life' changed for his 3.55 gears :)


Performance Package v6 Mustangs has 3.31 rear gear ratio :)
Thanks for the clarification on the gears, I knew the performance package gears was less than 3.55, I just couldn’t remember. I also couldn’t tell from his post if he was tuned or not. Anyway, never mind :cool:
 

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Discussion Starter #7
I believe he had his Bama 'tunes for life' changed for his 3.55 gears :)


Performance Package v6 Mustangs has 3.31 rear gear ratio :)
Yes thats right. I have the bama tunes for life. This problem is pre gear swap. The throttle body may be the issue. I'm going to disconnect my pedal commander this weekend and see if it improves it but otherwise, there is now IAC that I know on my car. I will have the TB completely removed and cleaned inside and out if i have to. I guess the mechanic only sprayed in there even though I told him to clean it last time.
 

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You need to remove it to really clean it good on the back. I replaced mine and the dropping has stopped or at least decrease substantially.

When I replaced mine it was shiny and clean on the front but then I saw the dark side. The back was filthy and there was a rim of gunk where the throttle plate stops.
 

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You need to remove it to really clean it good on the back. I replaced mine and the dropping has stopped or at least decrease substantially.

When I replaced mine it was shiny and clean on the front but then I saw the dark side. The back was filthy and there was a rim of gunk where the throttle plate stops.
Absolutely correct! Take the TB off and clean it. It’s a really simple DIY job. It’s a total rip-off to have a mechanic clean it. I clean my TB and MAF annually as part of my scheduled maintenance.
 
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