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LT1-LT4 Modifications 1993-97 Gen II Small Block V8

Need help on a sputtering problem

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Old Sep 20, 2014 | 10:14 AM
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Default Need help on a sputtering problem
I have a 94 z28 with the current mods:
3500 stall
Built Tranny
Full exhaust
CAI
1.6 RR
Hotcam
.030 bored
and a walboro 255 fuel pump.

My problem is the 1-2 shift and SOMETIMES the 2-3 shift.
When you put the car in first, and floor it, it gets to 5500-7000 and stars sputtering. same on the 2-3.


4-5 seconds is where its at.
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Old Sep 20, 2014 | 12:32 PM
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From: Jackstandican
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why are you shifting a hot cam at 7000 rpm? What springs do you have?
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Old Sep 20, 2014 | 12:58 PM
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Originally Posted by SS RRR
why are you shifting a hot cam at 7000 rpm? What springs do you have?
its not, it was in drive, and it never sputtered up top until the pcm went out and we got a flashed replacement. springs are rated @ 550, or 600. hes saying that somewhere in that rpm range it cuts out.
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Old Sep 20, 2014 | 01:10 PM
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Originally Posted by slownova73
, and it never sputtered up top until the pcm went out and we got a flashed replacement. .
....might want to speak with whoever tuned it

maybe the rpm shift point for the 1-2 shift needs to come down...as a guess

you could rule out fuel problem by taping a FP gauge to windshield and go for another "sustained WOT" run...it it drops, especially during your stumble....fuel pump and or wiring needs attention
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Old Sep 20, 2014 | 01:36 PM
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Originally Posted by ******
....might want to speak with whoever tuned it

maybe the rpm shift point for the 1-2 shift needs to come down...as a guess

you could rule out fuel problem by taping a FP gauge to windshield and go for another "sustained WOT" run...it it drops, especially during your stumble....fuel pump and or wiring needs attention
ill wait for wct13 to get back in here, he knows more about the new pcm and who tuned what.. the car drives great, has great power, till it hits that 5k-6k sweet spot and cuts up, disappears, then shifts and rolls on.
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Old Sep 21, 2014 | 01:22 AM
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From: Jackstandican
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Mine was opti related. Drove great everywhere in the RPM band until about 6500 and it would start to miss.
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Old Sep 21, 2014 | 01:43 AM
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Mine did something similar. I always thought it was the opti but it turned out I had valve float
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Old Sep 21, 2014 | 05:33 AM
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From: Jackstandican
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It would be a good idea to get a valve spring tester before throwing parts at it. You will only be able to test the first two cylinders on each side, but odds are, that should give you an idea of what's going on.
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Old Sep 21, 2014 | 03:44 PM
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The springs are rated at .650. The tuner said it was running 15 percent rich idle through wot. So he leaned it out and the sputtering got worse.

I dont think it done this until we got the new fuel pump
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