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Has this EVER happend before????HELP

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Old Jan 27, 2009 | 07:20 PM
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From: cassatt SC
Question Has this EVER happend before????HELP

I own a 2001 z28 mostly stock motor! When i shift letting off the gas it takes the next gears PERFECT but when i Power shift( hold the gas down) it throws the Random Missfire light... What would be causing this and Why only under WOT shifts? It Sputters and acts like its missing every cylinder and it KILLS HP... Its starting to scare me please any INFO on this is GOOD INFO! Thanks again CODY
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Old Jan 27, 2009 | 07:45 PM
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Anyone????
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Old Jan 27, 2009 | 08:08 PM
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See if your battery is rocking back because of a broken hold down and the pos terminal hitting the A/C accumulator.
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Old Jan 27, 2009 | 08:14 PM
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Just tried to shake it and its not moving! i shut the car off and read the codes again and NOTHING! but as soon as i WOT shift again it does it.... thanks tho
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Old Jan 27, 2009 | 08:26 PM
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look for any wires touching somwhere
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Old Jan 27, 2009 | 08:32 PM
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I'm not exactly sure what you mean by mostly stock, but my friend had turned up the line pressure in his GTO and it shifted so hard into the next gear the knock sensors would detect knock. Could be your sensors are showing a false misfire.
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Old Jan 27, 2009 | 09:06 PM
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I would guess low fuel pressure/volume. Your pump might not be able to supply enough fuel at high rpm wot shifts.
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Old Jan 27, 2009 | 09:23 PM
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Crazy **** man... my car is having almost exactly the same problem. Difference is if I shift below 6k there is no problem. If I power shift over 6 it feels like it just cuts out/bogs for a second then goes but if I let off even the slightest through a shift there is no problem. Hope you find your problem cause I've replaced my entire fuel system, plugs, wires, and had it tuned/dynoed while checking fuel pressure through one of the pulls all the way up to 6600 and everything looked ok, but it still does it when I shift
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Old Jan 27, 2009 | 09:31 PM
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From: cassatt SC
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urs is doing what mine is u describe it in perfect words nssane02 Please let me know if u find the reasonnnn!
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Old Jan 27, 2009 | 09:35 PM
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From: cassatt SC
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i have a diablo sport tuner if there is anything i can do to send it more fuel let me know cause i have NO idea how to tune my car with it i got it so my speed would be right with the gears in it
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Old Jan 27, 2009 | 09:42 PM
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Originally Posted by poolshark021
I would guess low fuel pressure/volume. Your pump might not be able to supply enough fuel at high rpm wot shifts.
Thats what I was thinking, how many miles on the motor?
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Old Jan 27, 2009 | 09:49 PM
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i had that problem... turned out to be the alternator wire getting burnt and shorting out of the alternator itself.... check for stupid stuff like that, also try changing plugs and wires.
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Old Jan 27, 2009 | 09:57 PM
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Originally Posted by MusTangKilla01Z28
urs is doing what mine is u describe it in perfect words nssane02 Please let me know if u find the reasonnnn!
I've been busting my *** trying to find the problem for about 2 months now with no luck. My fuel pressure holds right at 58 all the way to the limiter so that's ruled out and I was thinking the knock sensor idea sounded reasonable but it kicks just as hard when I shift under 6k so that's out and everything looked ok on the dyno so I'm out of ideas.

The engine stays at wot through the shift and never hits the limiter so I dont understand what is changing through the shift... I thought for a moment that maybe I was crazy and the clutch was just slipping, but it doesnt make any sense the way it's happening, and I got a couple inches of air on a launch this sunday so with that and a bunch of other reasons that was ruled out a long time ago.
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Old Jan 28, 2009 | 05:31 AM
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thanks guys the car has 101k on it... just order MSD wires and NGK plugs lets pray
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Old Jan 28, 2009 | 04:09 PM
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Valve Springs? They do get "tired" after a while, and might be giving up over 6K... or less if really old, tired and weak. So when powershifting, you know you're buzzing the engine pretty good..... maybe beyond the limits of the old springs.

Hey, just a thought.....

And BTW, if the lifters get pumped up, it'll take a second or two to recover.

Last edited by Scotty_82; Jan 28, 2009 at 05:09 PM.
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Old Jan 28, 2009 | 07:48 PM
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From: cassatt SC
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i should have the new wires on tomorrow along with the new plugs in i hope this fixes it! i hope i dont have to tear the motor down
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Old Jan 28, 2009 | 08:19 PM
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From: Houston
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I would at least check on ALL of the the electrical **** before I pulled the engine apart... although I'm getting close to that point as well Also if your problem is in fact the same as mine then it has to be something invoved with the quick shift since the engine itself will rev high without issue
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Old Jan 29, 2009 | 05:12 AM
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From: cassatt SC
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Yeah i can rev to the limiter and no problem when i shift a slower WOT shift but when i shift fast it does it for maybe the first 500-750 RPMs with NO power then its back to its normal self! i could always just shift slower but where is the fun in that lol Thanks everyone for your help so far!
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Old Jan 29, 2009 | 08:23 AM
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Abuse mode? Torque management?

I've never tried to powershift this car (and I never will)...but maybe one of those is your problem.
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Old Jan 29, 2009 | 09:11 AM
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No torque management on the T-56, never heard of "abuse mode"?
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