My Cobra is falling on its face hard while shifting from 3rd to 4th gear?

[Sweet '96 Cobra]

Lately My Kenne Bell 2.8H Mammoth powered '03 Cobra has had a problem under hard accelleration while shifting from 3rd to 4th and sometimes even 2nd to 3rd gear after coming up through all the gears under WOT.

Its tough to describe how it reacts but I'll do my best.

When it does what I mentioned above, which is not everytime. The car acts like the fuel is being completely shut off and it just dies and falls on its face HARD, mind you stays running. If I back out of the throttle and then get back on it, it seems fine? It doesn't have any problem if I just get into the throttle hard while in 3rd or 4th, it only does it while shifting from 3rd to 4th under WOT? If I powershift it never does it, only when I lift out of the throttle to shift.

I've monitored the pump duty cycle and fuel pressure with my interceptor gauge and they both seem normal when this occurs. Maybe later today if the weather clears up I'll get my brother to come along with me and we'll see if I can datalog it, my luck though it probably will work fine while we datalog it...lol

Do you guys think this might be a tuning issue?


My mods are in my showcase thread below..
http://mustangcanada.com/forums/mc-vehicle-showcase/7717-2003-svt-cobra-dsg-coupe-mammoth.html

My fuel system mods consist of:
-Dual focus pumps
-Kenne Bell Boost-a-pump
-RC 72lbs injectors
-PPRV Delete

 

[03cobra#694]

How`s your voltage?

 

[Sweet '96 Cobra]

How`s your voltage?

Not sure? Never thought to check that. Do you think I may have an alternator or charging issue?

 

[03cobra#694]

Not sure? Never thought to check that. Do you think I may have an alternator or charging issue?

It`s possible, log it and check your voltage and duty cycles.

 

[Teej281]

Tps maybe bad? I do suggest datalogging it though. Make sure everything is good.

 

[yellowgt02]

I think you should drive it out West and trade it for my Eaton.

That will solve all problems.
LOL.

I would Datalog it and see what you come up with.

 

[harvboi05]

replace the plugs. gap em correctly.

 

[jm@ReischePerf]

Sounds like the good old "hesitation" issue. Sometimes can show up out of the blue.

 

[harvboi05]

Sounds like the good old "hesitation" issue. Sometimes can show up out of the blue.

his PPRV has been deleted. thats why i suggested plugs, sounds like blow out to me, especially if his duty cycle % and etc look fine on the scan gauge.

 

[Sweet '96 Cobra]

It`s possible, log it and check your voltage and duty cycles.

Tps maybe bad? I do suggest datalogging it though. Make sure everything is good.

his PPRV has been deleted. thats why i suggested plugs, sounds like blow out to me, especially if his duty cycle % and etc look fine on the scan gauge.

Ok, what do you guys suggest for a plug gap? I cant remember what they're gapped at right now?


All good points here guys, much appreciated! I probably wont be able to datalog it tonight though as its still raining here.

 

[Sweet '96 Cobra]

Sounds like the good old "hesitation" issue. Sometimes can show up out of the blue.

Could you expand on that...Or are you referring to the PPRV?

 

[harvboi05]

Ok, what do you guys suggest for a plug gap? I cant remember what they're gapped at right now?

how much boost are you running? lots of people will say different things, and its kinda setup dependent, but anywhere from .028-.032 would probly work fine. plugs are only 16 bucks to swap em out, so its good maintenance regardless of its the problem or not and it just rules another thing out.

Could you expand on that...Or are you referring to the PPRV?

hes talking about the PPRV delete.

 

[Sweet '96 Cobra]

how much boost are you running?

15.5 psi right now. Going to turn it up again next spring though.

 

[harvboi05]

personally id go with a tight .030 or so. .028 will probly be just fine.

 

[stvdman]

Stock MAF still in there?

During my last tune I was told my MAF is "pegging out" at ~6600 rpm. When I am at WOT I get the same type of "falling flat" you describe at the top of 2-3, by that point I dont even stay in it for 3-4.

Just a guess though.

 

[mach1033]

Man I would have thought for sure it was a pprv issue. Also what plugs are you using? Did you change them when you lowered the boost?

 

[Sweet '96 Cobra]

Stock MAF still in there?
.

Yes it is still the stock MAF as the Mammoth kit is designed to use and my tuner said the MAF counts were still well within range. But who knows, it could be that? I usually dont rev mine past 6200-6300...

 

[Teej281]

Yea, if youre taking your car out that much...not really benefiting much out of that. And with a 2.8 KB you best be using a giant maf or at least a mafia maf extender.

 

[bubblehead93]

Did you recently reflash the pcm or disconnect the battery for any period of time. PCM learns corrections to the fuel pump voltage table that get cleared with a reset. I think if you datalog you will see a d/p spike after you let off the gas during the shift. Sounds like classic hesitation problem which the pprv delete does not fix 100%, you still have the underlying fuel pressure control problem which the pprv magnified. Need datalogs to be sure. Also is your frps output clipped in the tune, how about the associated P, I, and D terms, also did the tuner do anything with your voltage table after your fuel system mods (cut and pasting the adaptive values into the voltage tables after a suitable learning period). I'm no tuner, but I play with my pro-racer package and successfully got rid of my hesitation without pprv delete. Every car is different, datalogs are essential.

 

[03cobra#694]

I didn`t see you were running a stock maf. A/F`s?
As mentioned above, new maf or mafia.