HELP! High RPM miss!
09-30-2004, 05:53 PM
#1
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HELP! High RPM miss!
Ok so heres the deal. Car is missing up top, right at 5K and over. Car has the following done to it in the last year.
New Coil-------20K on it
New opti-------5K on it
New opti tubes
New plugs-----2K on them
New ICM
Spark Plug Wires have 40K on them
My friend rode in the car with me and he said it sounded and felt like a fuel issue.... It has stock injectors and stock fuel pump... Maybe thats the issue?? How can you tell a difference between a fuel related miss and an ignition related miss? I am so tired of fixing my car, I swear it breaks once a ****ing month.....Please help me.
Chris
New Coil-------20K on it
New opti-------5K on it
New opti tubes
New plugs-----2K on them
New ICM
Spark Plug Wires have 40K on them
My friend rode in the car with me and he said it sounded and felt like a fuel issue.... It has stock injectors and stock fuel pump... Maybe thats the issue?? How can you tell a difference between a fuel related miss and an ignition related miss? I am so tired of fixing my car, I swear it breaks once a ****ing month.....Please help me.
Chris
09-30-2004, 06:51 PM
#2
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Location: PA
Posts: 41
Re: HELP! High RPM miss!
Well, check my thread. I changed everything you did and the wires as well. Turns out my valve springs are too weak for my 1.6 rockers and gave out. I'd check the wires first and see if any are burnt.
Does it kind of almost die or sputter and then ok after the shift? My car started like that and then came the backfiring through the intake. All of this occurs at WOT only and right above 5000 rpms. I changed the springs and the problem is gone. The weak springs lead to valve float which can cause engine damage.
That was my problem, I hope your is more simple.
Does it kind of almost die or sputter and then ok after the shift? My car started like that and then came the backfiring through the intake. All of this occurs at WOT only and right above 5000 rpms. I changed the springs and the problem is gone. The weak springs lead to valve float which can cause engine damage.
That was my problem, I hope your is more simple.
09-30-2004, 07:52 PM
#4
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Re: HELP! High RPM miss!
Originally Posted by BiGGinZ
It could be something like a clogged cat or fuel filter. I would change the fuel filter because it is cheap and easy just so you don't spend any more money if it was that.
Sorry i forgot to say that it has a new fuel filter, and the cat is fine....... I have LT4 valvesprings.... Shouldnt those be fine???
09-30-2004, 08:42 PM
#5
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Re: HELP! High RPM miss!
Even though you say you have a new ignition control module you might think about taking it off and having it tested might not hurt to heat it up alittle with a blow dryer then have it tested. Just cause its new doesnt mean it isnt faulty.
10-01-2004, 07:53 AM
#6
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Re: HELP! High RPM miss!
Yes,
LT-4 springs should be fine. How about checking the fuel pressure at WOT in the upper rpm range. I used my fuel pressure guage and duct taped it to the windshield and had someone watch the guage as we approached 5000 rpm's at WOT to eliminate any pump issues.
LT-4 springs should be fine. How about checking the fuel pressure at WOT in the upper rpm range. I used my fuel pressure guage and duct taped it to the windshield and had someone watch the guage as we approached 5000 rpm's at WOT to eliminate any pump issues.
10-03-2004, 04:26 PM
#8
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Re: HELP! High RPM miss!
Originally Posted by DarkHorse
My upper RPM miss was caused by a bad MAF. Once the dealership replaced that, all was good.
May want to borrow a MAF from a friend and try that first.
May want to borrow a MAF from a friend and try that first.
Its got a new maf too.........
Well my car overheated the other day and it started doing this after that..... So my friend said that i could have melted a spark plug when it got too hot..... But wouldnt that cause it to miss all of the time instead of just up top?? I dunno.... This is frustrating.
10-03-2004, 04:37 PM
#9
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Re: HELP! High RPM miss!
not necessarily. WHen my plugs were bad, i had a high rpm miss with backfire, it kept getting worse.
Im thinking the plug can operate at low rpm, but at higher rpm, it cannot deliver the spark so many times in 1 second because the contacts are bad, so some times there is no spark and that gives the miss.
If the plug was completely shot, then yeah, you'd be running on 7 cylinders which is always noticeable.
Im thinking the plug can operate at low rpm, but at higher rpm, it cannot deliver the spark so many times in 1 second because the contacts are bad, so some times there is no spark and that gives the miss.
If the plug was completely shot, then yeah, you'd be running on 7 cylinders which is always noticeable.
10-03-2004, 04:49 PM
#10
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Re: HELP! High RPM miss!
I wonder if oveheating could ruin the spring pressure. Also if you overheated you might have sprung a leak in the head gasket that is only apparent at high rpm when the waterpump is putting lots of pressure on the cooling system. The coolant would kill the combustion and theres your misfire. I am just making some guesses however so dont get too worried. Could just be a coincidence and the opti went at the same time you overheated.
Last edited by turbo_Z; 10-03-2004 at 04:58 PM.
10-03-2004, 11:07 PM
#11
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Re: HELP! High RPM miss!
I had the same problem about 2 years ago on my Z, plug wires only had 12k miles on them. Drove car with fuel pressure gage hooked up, ok. Checked for arching from wires at night found no arching. Car ran great except cut out at high rpm, couldnt figure out problem. Opti was recently replaced, plugs, coil, ICM, and fuel filter. Went to Auto zone and spent $29.00 on new set of plug wires, problem fixed. Hope this helps, this was my problem.
10-04-2004, 10:12 AM
#12
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Re: HELP! High RPM miss!
Thanks alot guys, I think I am going to change the plug wires. And if that doesnt work then i will just have to go from there... I appreciate all of the responses guys, our damn LT1's and our ignition problems! 
Chris
Chris
10-04-2004, 02:57 PM
#14
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Re: HELP! High RPM miss!
Originally Posted by anilator
One other thing to check. Make sure that the two wires that connect to the coil (+,-)are on all the way and are not slipping off.
Cool, thanks.
10-05-2004, 02:39 AM
#15
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Re: HELP! High RPM miss!
Figured out the problem. Car is fixed..... I thought i had traced all of the wires to make sure that they werent arching but it seems that on wire was clear of the header when it was sitting idle but it rubbed the header and arched under WOT.... So i twisty tied it for free and its FIXED!!! **** yeah!. Thanks for all of the help guys, sometimes its the easy stuff you overlook!
Chris
Chris