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Discussion Starter #1
Car pulls hard throughout the RPM range until it reaches 90mph and then it starts to sputter. Any ideas of what to look for besides not going 90mph? Going through the gears is fine until it reaches that speed. It is only around 4200 rpm at that point.
 

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It would help readers greatly if you'd state just what the car is ??

Is it a stock GT
Does it have a tune
A Saleen, or a Saleen with supercharger.
 

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Discussion Starter #3
The car is 06 GT. The following has been done many years back:
BBK 62MM Throttle Body W/ Spacer
MMR GT Annihilator Intake w/ High Flow Intake Tube
Steeda Underdrive Pulley System
Ford Racing Stinger Axle Back Exhaust Kit.
4.10 Ford Racing Ring Gears
SCT Livewire Flash Tuner with custom tune for above items.

It has worked and performed well with no issues before. The car doesn't get a lot of miles on it as were currently just turned over 24,000.
Thanks for any help provided.
 

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Car pulls hard throughout the RPM range until it reaches 90mph and then it starts to sputter. Any ideas of what to look for besides not going 90mph? Going through the gears is fine until it reaches that speed. It is only around 4200 rpm at that point.
Sounds like you're in 4th gear when that happens. Does the engine splutter at 4200rpm in 1st, 2nd, and 3rd as well?
Use your SCT tuner to scan the ECU for fault codes. You might then pinpoint the problem.
 

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First post says it runs fine throughout the RPM range, until you hit 90 mph . . . . assuming that means it runs fine at 4200+ RPM in lower gears:

One wild guess is some kind of turbulence in the intake caused by high speed incoming air, messing up the Mass Air Flow sensor . . . take a look at how the air enters the intake and see if that might be it. I think it should throw some codes if that is it.
 

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Sounds like its running out of fuel. When's the last time the fuel filter was changed? If not that, I'd have the fuel pressure monitored and see if it goes awry around that speed.
 

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Who wrote the tune? auto or manual?

-Matt
 

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Sounds like its running out of fuel. When's the last time the fuel filter was changed? If not that, I'd have the fuel pressure monitored and see if it goes awry around that speed.
+1
I don't know about anyone else's experience, maybe it's just my area's gas (?) but I find the fuel filters (Motorcraft) to be pretty clog-prone. Seems like I'm replacing mine a lot. (If I was very bored I suppose I could put a fuel pressure sensor on the back-end side but...well...I'm also lazy... :p )
 

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Sounds like its running out of fuel. When's the last time the fuel filter was changed? If not that, I'd have the fuel pressure monitored and see if it goes awry around that speed.
If the engine was running out of fuel, it wouldn't just happen at 4200rpm in 4th gear.

JBert said:
One wild guess is some kind of turbulence in the intake caused by high speed incoming air, messing up the Mass Air Flow sensor . . . take a look at how the air enters the intake and see if that might be it.
I think you're onto something there.
 

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Discussion Starter #10
It is in fourth gear when this happens. The tune is through American Muscle. It has preformed flawlessly in the past but again the car sits for long periods of time and it doesn't see that speed very often. I'll check the codes to see if there are any.
 

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If the engine was running out of fuel, it wouldn't just happen at 4200rpm in 4th gear.

It very well could. Engine is much more loaded in a higher gear. Car has worked flawlessly in the past as he said. So its a new problem.

Car is sputtering so its either air, fuel or spark problem. My bet is on fuel. Cheap filter and monitoring the fuel system for a pull is cheap and easy and would rule it out.
 
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