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10-01-2008, 11:59 PM
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#1
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Guest
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High RPM miss fire
any idea what it could be guys? its a head/cam LT1. could the stock fuel pump just not have enough to feed it?
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10-02-2008, 09:48 AM
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#2
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NJFBOA Co-Founder
Join Date: Jul 2004
Location: All up in your kool aid!
Posts: 12,235
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Pull a plug and check it. If it doesn't have the light brown haze on it you are leaning out.
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10-03-2008, 09:45 PM
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#3
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Guest
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would that cause it to break up in high rpms though? almost like the power cuts out and then comes back in
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10-03-2008, 11:02 PM
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#4
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Meet Coordinator
Join Date: Jan 2008
Location: brick/pt. pleasant beach
Posts: 19,366
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is it tuned?
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10-04-2008, 12:44 AM
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#5
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Guest
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yes
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10-04-2008, 09:36 AM
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#6
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Sliderule / Moderator
Join Date: Oct 2004
Location: Catawissa PA
Posts: 2,294
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So does it have a mis, or is it cutting out? Also howh high in to the RPMs are you when this mis/cutout occurs?
If it's actually cutting out then I'd guess first that you might be bounching off thr rev limiter. A miss could be a weak coil or Opti, even the gap on the plugs.
A stock FP will handle near 400 HP without a problem, if it's in good shape.
__________________
93Z M6 Black: The 385 Lives! Supercharged, 3-core front mount intercooler, GTP heads, 3:73's, Street twin clutch, Jethot Longtubes, Mufflex 4" catback/spintech, S+W cage, Spohn Suspenion, Yada Yada Yada
1) Build it
2) Race it
3) Break it
4) Repeat!!!
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10-04-2008, 07:36 PM
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#7
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Guest
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feels like its cutting out to me, Ron said it feels like a miss. its over 4k but def not the rev limiter. the car should be putting near 400 to the wheels
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10-05-2008, 02:42 PM
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#8
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12 Second Club
Join Date: Sep 2004
Location: Vineland
Posts: 928
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The way to know if its your fuel would be first to put a gauge on it, tape it to the windshield, and drive it...watch for a drop in fuel pressure when your "miss" occurs. second, a datalog at high RPM couldnt hurt...you would be able to see injector pulse width and see if they are static at your "miss" and beyond. If you have means of doing so, let me know and I'll dig up the formula for injector duty cycle for you.
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87 iroc with the usual go fast stuff
heavier than your half ton.
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10-05-2008, 02:50 PM
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#9
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,936
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Sounds like a coil to me.
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Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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10-10-2008, 07:48 AM
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#10
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Join Date: Oct 2008
Posts: 19
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Quote:
Originally Posted by IROCdan330
If you have means of doing so, let me know and I'll dig up the formula for injector duty cycle for you.
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Here you go.. with an online calc to figure it out. 
http://www.injector-rehab.com/kbse/idc.htm
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Fuel Injector Cleaning and Balancing
www.Injector-Rehab.com
I was... well... I was trippin balls, so I decided to get on my bench grinder...
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10-23-2008, 08:32 PM
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#11
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10 Second Club; Has fan club
Join Date: Dec 2005
Location: Delmont nj
Posts: 4,369
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id say its in between a miss and it cutting out. its not violently bucking, but its definately noticeable in the upper rpm range 4500+
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01' Z06 62k miles. Vararam, Longtubes, off road xpipe, tuned by me. Times TBA
2001 Corvette, Bolt ons , tuned 10.75@124.56 mph 1.38 60' Sold
1997 Saturn Sc1 5spd DOHC swapped
Bolt ons, decked head, stock intake cam on exhaust side, lotsa weight redux
13.22@102.32 mph 1.93 60'
12's on moda? One day
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10-23-2008, 09:24 PM
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#12
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,936
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Borrow a coil and throw it on there. And your not getting any opti death alerts are you?
__________________
Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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10-24-2008, 12:21 AM
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#13
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Guest
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no it runs fine other then that, the car is almost back together so well see how it is with the new fuel pump in it... now if only i could get a real day off lol
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10-24-2008, 03:42 PM
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#14
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,936
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And of course, its always a perfect excuse to get a new MSD or likewise coil.
__________________
Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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11-03-2008, 02:28 PM
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#15
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10 Second Club
Join Date: Aug 2004
Location: Hatfield, PA
Posts: 1,292
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id say go entire MSD ignition on the car. are you running nitrous? what are the gap on the plugs?
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11-03-2008, 02:38 PM
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#16
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,936
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MSD opti is iffy in its price tag being worth it. But spark plug wires, coil and 6AL are all good stuff.
__________________
Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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11-04-2008, 11:58 AM
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#17
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Join Date: Nov 2004
Location: Randolph
Posts: 198
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I'd remove and inspect each plug wire, chances are you'll find one that got too close to the header primary and got toasted.
__________________
1982 Z28 w/ '01 LS1 + T56, TR224 cam, Katech oil pump, JWIS chain
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11-05-2008, 07:35 PM
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#18
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Join Date: Sep 2008
Location: Edison, NJ
Posts: 70
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Quote:
Originally Posted by Pampered-Z
So does it have a mis, or is it cutting out? Also howh high in to the RPMs are you when this mis/cutout occurs?
If it's actually cutting out then I'd guess first that you might be bounching off thr rev limiter. A miss could be a weak coil or Opti, even the gap on the plugs.
A stock FP will handle near 400 HP without a problem, if it's in good shape.
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I'd vote opti but without experiencing it no way to be sure. opti's an expensive guess.
__________________
1992 Camaro, 2x3 chassis, all fiberglass except quarters and roof. 8.864@154.1
1969 Camaro RS/SS 396/350HP, stock frame off restoration
1997 Camaro SS, stock.
1987 Buick Grand National, 11.85@115, 18,500 original miles
1987 Buick Grand National (old car, still drive/tune for the new owner), 9.20@150
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11-19-2008, 08:20 PM
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#19
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Guest
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well the car is back on the road with the new fuel pump in and it seems to be fixed as far as cutting out. there just seems to be a slight break up up top now and i think its tuning because it smells so mad like fuel that its burning my eyes. time for a 58mm TB, AFPR and a dyno tune
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