High rpm miss!!!!! HELP!!!!!
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High rpm miss!!!!! HELP!!!!!
Ok,93 c4 w 39k,6 spd,imac condition,just did ARH long tubes,magnaflow cat back,air foil,moded air box,& my computer tuned by pcms for less.. And let me say wow what a diff!!! But after a few miles of driving it where it pulled hard all the way to 6000 rpm,it started cutting out at about 5500 up. So I figured it was the stock plug wires,replaced them and seems much better bu still a lil miss over 5500,enuf to really bother me.. Any ideas??? Could it be the coil thing,multi spark or whatever it's called?? I JUST WANT IT TO RUN SMOOTH TO THE REV LIMITER!!!!!!! Please help.. Thanks..
Last edited by ASRmotors; Apr 27, 2013 at 02:24 AM.
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From: Slidell Louisiana
What speed is the limiter set at now.
From your post I'm getting that it was pulling smoothly to 6K or higher now it doesn't.
Are you on stock heads and valvetrain?
I'm wondering if you experienced valve float..
It could be so many things,
Could be the OPTI, tune, valve float or you could be hitting the rev limiter. (factory tach is not a precision piece)
Can you datalog? A datalog may exactly where its falling over.
That's what I do on a fresh build run some datalogs send them to the tuner and if all is well he tweeks the tune, or I get an email say hey Mike its mechanical fix your ****.
Mike
From your post I'm getting that it was pulling smoothly to 6K or higher now it doesn't.
Are you on stock heads and valvetrain?
I'm wondering if you experienced valve float..
It could be so many things,
Could be the OPTI, tune, valve float or you could be hitting the rev limiter. (factory tach is not a precision piece)
Can you datalog? A datalog may exactly where its falling over.
That's what I do on a fresh build run some datalogs send them to the tuner and if all is well he tweeks the tune, or I get an email say hey Mike its mechanical fix your ****.
Mike
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All stock except for bolt ons. and yes when I first drove it after installing all the parts,headers etc,the first few times I ran it,it ran hard and smooth to 6000,then it started missing really bad after 5000,figured it had to be the stock plug wires,thats just what it felt like. So new wires,and again ran great for a lil bit,now the miss is not as bad but after 5500 is there.. The car ran low on gas,& then really ran like **** so im wondering If I just haven't ran the old gas out of it maybe?? As far as the rev lim. I don't know what they set it at,i didn't get a spec sheet or anything,Im guessing its 6500?? If you hold it on thru the miss it will still rise to 6000 just not smoothly... Im leaning on a weak optispark,but this is my first chevy so IDK... any more help or suggestions are appreciated... thanks
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Joined: Jan 2005
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From: Slidell Louisiana
All stock except for bolt ons. and yes when I first drove it after installing all the parts,headers etc,the first few times I ran it,it ran hard and smooth to 6000,then it started missing really bad after 5000,figured it had to be the stock plug wires,thats just what it felt like. So new wires,and again ran great for a lil bit,now the miss is not as bad but after 5500 is there.. The car ran low on gas,& then really ran like **** so im wondering If I just haven't ran the old gas out of it maybe?? As far as the rev lim. I don't know what they set it at,i didn't get a spec sheet or anything,Im guessing its 6500?? If you hold it on thru the miss it will still rise to 6000 just not smoothly... Im leaning on a weak optispark,but this is my first chevy so IDK... any more help or suggestions are appreciated... thanks
Contact your tuner and see what he set the rev-limit at.
IRT your original post, check your fuel pressure, the plugs, and wire routing.
Test your coil, ICM
Change your fuel filter, and plugs if they are original. I'm still not certain your not feeling valve float, or fuel starvation or a tired ignition ....
Datalogging would give you more info...
But I'm going to repeat....
If you really want to pull to 6K reliably at a minimum change your valve springs or someday soon there will be another I need to cheaply rebuild my LT1 thread or I'm parting out my 93....
Mike
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Im not tryn to hit 6500,I know its not even makn power over 6000,I just want it to hit 6000 smooth and fast like it did at one time.. What do you think about the one sugg. to change the coil?? could the coil make this issue but run fine otherwise?? If its cheap & easy like he says Im gna try that first I guess,and another set of plugs.. Is there a GOOD spark plug for my car that I should be using???? Thanks guys.. Oh ya im gna do the fuel filter too... cheap..
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From: Louisburg NC
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Thanks,is the MSD a stock replacement or does it mount different,do you have to modify anything to install it?? if its direct bolt on like stock I allways like to get the better quality stuff,just don't like to change to much ya know??
Racer
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From: Louisburg NC
Unless you have a couple of hours to **** away for no reason.
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So I'm a body @ paint guy mostly,was wondering if u could tell me what's involved in changing the valve springs,,,do you have to remove heads? Or just pop off valve covers & easy goes it... Thanks for the input...
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From: O'Fallon Missouri
If you are still running the stock valve train at 39k miles, the valve springs should be fine.
Valve springs can be changed with heads on the engine, I'm on my fourth set. You can bring each cylinder to TDC to keep the valves from falling, or stuff rope in the cylinder. I would also suggest changing the valve seals while you're in there.
Valve springs can be changed with heads on the engine, I'm on my fourth set. You can bring each cylinder to TDC to keep the valves from falling, or stuff rope in the cylinder. I would also suggest changing the valve seals while you're in there.
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Does changing the valve springs let it rev higher,easier,or is it something you do when they get weak or worn out say with higher miles?? Im just wondering if its going to make any diff in how it runs & if its worth it when down the line im probly gna do cam and alum heads..... Im hoping the MSD coil coming will stop this lil hiccup,its not that bad,It just doesn't sound like valves floatn,more like a weak spark up high or one cyl missn.. IDK .. AGGGHHHHHHHH!!!!!!
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Can you recommend a good spring set up as far as brand or whatever? Also do you Think this is something that I should have a good Chevy mechanic do Or is this something that I can pull off myself at my shop? It doesn't sound too hard I've just never done it before.