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Diagnosis Please

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Old 07-14-2010, 08:04 PM
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ffk_pennywise
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Had something weird happen on my way to work today. I slowed down through a construction zone and putted through it in 4th gear. Hit the end of the zone and hopped on the gas while getting back in the fast lane. About 40-45mph and all the sudden it felt like something slammed, like it slammed into gear or something, and it got this sudden burst of power. I even heard a clunk. It was pretty strange but I kinda just filed it away in my head and continued on without issue. So on the way home I coast down the exit ramp to the outer road leading to my house and at the bottom of the road I shift into 3rd and off up the outer road I go. The speed limit is 45 on this road and as I'm at 40-45mph again it suddenly gets this burst of power. Not nearly as harsh this time as I'm nearly the speed limit and lightly on the gas. I was in a different gear this time too remember, but the same speed as last time. I tried to duplicate the problem this time but could not. My mods are in my signature. Basically an 87 Brenspeed tune, Intake, and Delete Plates. Been running strong since November '06. 82k miles on her. Anyone have any idea what could be going on? I'm not afraid to wrench on the car at all, I installed all my mods, but I'm not so good with troubleshooting engines unfortunately.
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Old 07-14-2010, 08:07 PM
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SpartaPerformance
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Sounds like bad motor or trans mount from how you describe it.
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Old 07-14-2010, 08:09 PM
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ffk_pennywise
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How would a bad mount give it a sudden jolt of power? I was thinking more like a plug going bad or something. I'm all ears though.
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Old 07-14-2010, 08:16 PM
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incorrigible
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Might want to try reloading your tune.
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Old 07-14-2010, 08:21 PM
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ffk_pennywise
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You know I sort of forgot about this but about a month ago I had a brief issue with the RPM's dropping when i eased off the clutch during take off. I found myself having to give a bit more gas than usual. It quit after a few days though. Not sure if its related, but the more info the better right?

I'll try reloading in the morning. Certainly cant hurt.
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Old 07-14-2010, 11:25 PM
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thedrod
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Have you read the TSB for the fuel pump issue? It is written for 2005-2006 Mustangs, but my buddy with a 2007 had the issue as well.

I experienced it as well. After driving on the freeway, then slowing down, if I were to give it gas it would jolt as it lost fuel, then got fuel, then lost fuel, making it buck down the road for a bit. Check it out.

https://mustangforums.com/mustang-ts...NG-CRUISE.html
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Old 07-15-2010, 07:08 AM
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Nuke
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It doesn't sound like the fuel pump to me since that would appear as hesitation and bucking. I'm thinking something related to the delete plates or the phasors, what with your description of a sudden power burst. Unfortunately, I couldn't begin to tell you how to verify that it's either of those.
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Old 07-15-2010, 08:50 AM
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ffk_pennywise
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Yeah no hesitation or bucking. Plus the first time it did it was after only 20 minutes or so of driving. Who knows. Maybe I'll get lucky and it'll explode and i'll put brenspeeds 302 and a blower in.
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Old 07-15-2010, 10:10 AM
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jiga
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Originally Posted by thedrod
Have you read the TSB for the fuel pump issue? It is written for 2005-2006 Mustangs, but my buddy with a 2007 had the issue as well.

I experienced it as well. After driving on the freeway, then slowing down, if I were to give it gas it would jolt as it lost fuel, then got fuel, then lost fuel, making it buck down the road for a bit. Check it out.

https://mustangforums.com/mustang-ts...NG-CRUISE.html
Same exact problem I am having right now. Once I get some free time I need to take mine in.
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Old 07-15-2010, 01:48 PM
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SpartaPerformance
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Originally Posted by ffk_pennywise
How would a bad mount give it a sudden jolt of power? I was thinking more like a plug going bad or something. I'm all ears though.
To me the way I read it sounded like you hit the gas heard a clunk then the car took off. If the mounts are bad you can have a split second of what feels like a loss of power as the engine physically moves from torque instead of transmitting torque through the drivetrain.
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