high rpm miss

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Jun 27, 2009 | 04:52 AM

theslow00

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From: surprise az

high rpm miss

well guys i have a problem and need to figure it out. just had the car tuned and dynoed. what is happening is in 2 spots 4500 rpm it falls a little and the a/f goes from 12.8 to 13.3 and at 6000rpm a/f goes from 12.9 to 13.4 it falls flat like a dead cylinder you can here it in the exhaust like a rev limiter, can feel it to. it is not vavle float i would see it in the graph like a waterfall effect but it just falls flat -30hp and flat lines. the guy who tuned my car knows what he is doing and the a/f it perfect across the board. i am not pulling any timing anywhere in the pulls or anything, no knock nothing. tomorrow i am going to change out some coils it is the only thing i can think of. i have brand new plugs tr6 gaped at .35, new wires (which i am going to change again just to change ) and hopefully will fix it. any other thoughts? by the way it is a ls1 thx mike

Jun 27, 2009 | 09:40 PM

theslow00

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From: surprise az

well i changed the coil packs and the same thing is going on i am stumped

Jun 27, 2009 | 11:30 PM

Duffster

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if the afr abruptly changes, on a WOT dyno run, you need to check tuning AGAIN.

Jun 28, 2009 | 12:27 AM

theslow00

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From: surprise az

the thing is that is acting like it is hitting the rev limiter but it isnt.

Jun 28, 2009 | 01:41 PM

theslow00

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From: surprise az

bump...

Jun 30, 2009 | 12:18 AM

myslow92

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From: wish I could remember

Quote:

Originally Posted by Duffster

if the afr abruptly changes, on a WOT dyno run, you need to check tuning AGAIN.

not in the tune....tune is SOLID
the af ratio does not change due to the tune I saw the screen as it was making pulls

it changes due to something else

this car just drops 30-40hp like a rock at exactly 6k it drops so fast it follows the vertical line on graph that is the 6k mark.....strangest **** in the world the car pulls strong and then hits 6k and

Jun 30, 2009 | 02:02 AM

LS6427

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From: South Florida

spark plug wire touching an exhaust manifold pipe. Happens to the best of us, check it out.

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Jun 30, 2009 | 10:14 PM

myslow92

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From: wish I could remember

part it out and buy new car.........I will take the heads off your hands

j/k

Jun 30, 2009 | 10:34 PM

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theslow00

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From: surprise az

i think i might have figured it out. i found that i am running to long of pushrods ( 7.350 ) and i need to be running ( 7.325 ) hopefully that will fix the issue. crossing fingers

Jun 30, 2009 | 10:37 PM

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CTSV_510

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I had the same problem and it was in the tune.

My new tuner fixed it without having to change any parts.

I'm not saying you need your tune adjusted, I'm just saying.