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Discussion Starter · #1 ·
Go to this webpage:

http://www.x2cmotorsports.com/X2CMovies/

Listen to the 2-3 shift in this video:

"03 Cobra @ Carlsbad II, 3.1mb video"

OR, the 3-4 shift in this video:

"03 Cobra @ Famoso, 9mb video"

Who else has this hesitation and what will cure it? Funny enough I did (2) 0-120 blasts today and noticed it on the first run through the gears but not the second... very confused!
 

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I have the same problem also. It happens under certain conditions, but not all. It use to be really bad until I disconnected my boost dump and now it is no where near as bad. There might be also a second cause stated by mjchip which has to due with the returnless fuel system being incapable of responding to such high fluctuations in manifold pressure.
 

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Discussion Starter · #3 ·
I'll have to try to boost dump but don't think thats it given I had TC off in both cases but hey thats free to try! Thanks for the input!
 

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Jerry said:
I'll have to try to boost dump but don't think thats it given I had TC off in both cases but hey thats free to try! Thanks for the input!
The boost dump has nothing to due with TC under normal operation. TC only uses the dump when wheel slip is noticed and it is on. I "never" drive with TC on unless I forget to turn it off. The boost dump is controlled by the PCM and uses it to dump boost under certain conditions including when you are shifting in boost and when the PCM detects "abuse". The Lightening guys had major problems with it and regularly disable it for this reason.

I just disconnect the wiring harness to the dump valve it is the easiest way and doesn't mess up anything.
 

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Discussion Starter · #5 ·
Understand and agreed.. I've disconnected it via the connector like you said when I was chasing a different problem.. I have no problem doing that again!
 
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My moms 03 Cobra vert with the KB on does that too....even though the traction control is off.....then at times...I will bang second and if feels like the Traction Control came on....then I would hit the TC switch on and off and then on and off and try again...and all is fine. Really screwy..and not good when you are trying to race someone. Not good at all.....My 03 and my dads 03 have never done this......its like the computer isnt reading the TC switch right or something.

Harry
www.HotRodHarrys.com
2003 Cobra (Dark Shadow Grey)
 

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I always thought I was brushing the rev limiter or the boost dump was a factor. Well then Rick raised the limiter in my previous burn and took care of the boost dump in the chip, and just for good measure I unplugged the sensor, and I will get it some of the time, always 2-3 and 3-4 if I dont shift smoothly when trying to powershift, I knew there had to be something else to this problem because I didnt think I was on the limiter. Some of the big dogs on here need to chime in!!!
 

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Snake Charmer
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Im at 9psi myself and havent noticed it, maybe I will at 17psi. I have the KB setup so it doesnt dump boost.
 

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After MANY hours of investigation, we now have a pretty good understanding of this problem and what causes it. We are also working on a potential solution. However, it is an inherent shortcoming of Ford's implementation of the returnless fuel system on this car so it is questionable if we can TOTALLY eliminate the hesitation. I'm pretty sure that we can eliminate the major issue of the PCM pulling power due to seeing erroneously low fuel pressure in an effort to save the motor.

You can read more about it here:

http://www.svtperformance.com/forums/showthread.php?s=&threadid=42772

Best,

MJ
 
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On my moms 03 it isnt a hesitation though....and it only happens when power shifting.......my case is definitely the traction contol...cause the car did it stock too ..with the TC off.

Harry
 

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If its of any correlation, my 01 Cobra hesitates sometimes on a hardshift. I was under the impression that the PCM was pulling timing like the 94-95 Mustang computer did. On my 95 there was no hesitation, you could just tell the car wasn't at its potential.

Most noticably on my car, the 1 - 2 shift, it almosts feels like the traction control comes on.
 
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Eric Brooks said:
If its of any correlation, my 01 Cobra hesitates sometimes on a hardshift. I was under the impression that the PCM was pulling timing like the 94-95 Mustang computer did. On my 95 there was no hesitation, you could just tell the car wasn't at its potential.

Most noticably on my car, the 1 - 2 shift, it almosts feels like the traction control comes on.
Hmmmmm...thanks Eric...my mom doesnt power shift and it doesnt happen to her....only me :D So I guess....I will just stop power shifting her car now :rolleyes:

Hot Rod(I will do all my powershifting in my car..awesome!)Harry
www.HotRodHarrys.com
 

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Hot Rod Harry said:
Hmmmmm...thanks Eric...my mom doesnt power shift and it doesnt happen to her....only me :D So I guess....I will just stop power shifting her car now :rolleyes:

Hot Rod(I will do all my powershifting in my car..awesome!)Harry
www.HotRodHarrys.com
Beating on your mom's car how could you.:evil
 

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Discussion Starter · #14 ·
Hot Rod Harry said:
Hmmmmm...thanks Eric...my mom doesnt power shift and it doesnt happen to her....only me :D So I guess....I will just stop power shifting her car now :rolleyes:

Hot Rod(I will do all my powershifting in my car..awesome!)Harry
www.HotRodHarrys.com
Harry, see the other thread.. you may be flat out powershifting your own car but not your mom's.. its the fast but still lift throttle shifting that causes this. See guys, Harry DOES treat his Mom's car slightly better than his own :)
 
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Jerry said:
Harry, see the other thread.. you may be flat out powershifting your own car but not your mom's.. its the fast but still lift throttle shifting that causes this. See guys, Harry DOES treat his Mom's car slightly better than his own :)
LOL.....

Harry
 

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Hot Rod Harry said:
......my case is definitely the traction contol...cause the car did it stock too ..with the TC off.

Harry
I'm confused....you say that in your case it "is definitely the traction control" and yet you say that your car did it when stock "with the TC off.". So Harry, if your car did it with the TC off what makes you think that in your case it's the traction control kicking in?

MJ
 
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mjchip said:
I'm confused....you say that in your case it "is definitely the traction control" and yet you say that your car did it when stock "with the TC off.". So Harry, if your car did it with the TC off what makes you think that in your case it's the traction control kicking in?

MJ
Not my car...mine never did it..stock or modded....it just plain goes!

But my moms 03 ...with the TC switch turned off would at times just stop once power shifted or even just shifted fast....of course it would do it if I would forget to turn the TC off......but even with that stupid switched turned off...it would do it sometimes...not all the time....it is nothing to do even with powershifting...its in that switch I think.....If I hit it off...then get on it and bang second...it might do it...then I will try again....it will do it....then I will hit the TC switch on and off a few times and then try again...and its fine...again and its finee......really screwy. Like I said...it did this stock too come to think of it. Sorry to turn this post into this...I think the original post is just a lag or something.

Harry
 

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My car has the same hesitation on hard "quick lift" shifts to any gear.

Just like twofast4u said "I never drive with TC on unless I forgot to turn it off".

I had posted about this issue before and people suggested that I upgrade my plugs to Denso's (I was running the stock plugs re-gapped to .038). I did the upgrade and the only difference the plugs made was a smoother idle. I have driven several stock Cobra's and never had this happen. After trying many different shift methods the only way I have found to eliminate the "hesitation" is to slow the shift speed down:hammer (I didn't try power shifting on this car yet the strength.....or should I say lack of.......of the IRS just scares me).

I hope someone comes up with a fix for this problem because it is annoying at hell!!:mad: :mad:
 

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Jerry,

You weenie. Just powershift and be done with the problem or do what I did and spend too much money swapping to a return style fuel system. ;)

John
Novi'd 99 Cobra
 

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Discussion Starter · #20 ·
Maynor said:
Jerry,

You weenie. Just powershift and be done with the problem or do what I did and spend too much money swapping to a return style fuel system. ;)

John
Novi'd 99 Cobra
A reminder for the master gear grinder himself: C5 coupe! Couldn't put that car away because he couldn't hit any of the 3 gears ;) I know I know.. it was the plastic clutch pawl but I couldn't resist!
 
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