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10-02-2009, 11:36 PM
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#1
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I, Vettezuki
Join Date: Feb 2006
Posts: 14,754
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Need Help Diagnosing Poor Running
Took the Vette out tonight to go to the gym. It sounded funny, and was WAY down on power. I'm guessing a couple, maybe few cylinders are not firing. However, the check engine light did not come one. If so the cylinders in question are either not getting spark or fuel, or both. For those who don't know my Vette, it's a Frankstein H&C LSx motor setup basically like a 2001 F Body.
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10-03-2009, 03:53 AM
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#2
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Senior Member
Join Date: Jun 2009
Posts: 2,509
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Id check the plug wires.
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93 GMC Typhoon: new money pit/PITA. Now GT3788R powered.
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"If it has tit's or tires, you can be pretty sure your going to have problems with them..."
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10-03-2009, 10:45 AM
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#3
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Fast & Filthy
Join Date: Jun 2008
Posts: 3,840
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Quote:
Originally Posted by Damian
Id check the plug wires.
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Same here. This is the same issue I just went through with the Cobra. Check to make sure that none of the wires are sitting on the exhaust. Another way to check if the plug wires are arcing is to get a spray bottle and fill it with water. Pull your car in the garage where it's a little darker and lightly spray water mist near the wires. If any are bad you'll see the spark arc through the mist.
If the wires are fine pull the plugs and make sure the porcelain looks good. When we were putting the 383 in Phil's Jimmy we had one plug that the porcelain was loose and it was arcing causing a misfire. You couldn't tell it was loose by looking at it but when you held it you could feel it. |
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10-03-2009, 08:20 PM
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#4
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I, Vettezuki
Join Date: Feb 2006
Posts: 14,754
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Thanks guys. I'll check this out tomorrow afternoon and report back.
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10-03-2009, 08:35 PM
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#5
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Resident Avatar Gambler
Join Date: Nov 2006
Posts: 5,997
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Quote:
Originally Posted by Vettezuki
Thanks guys. I'll check this out tomorrow afternoon and report back.
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Paul said two other possibilities would be a bad coil pack, or clogged cats.
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Insanity: doing the same thing over and over again and expecting different results.
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10-03-2009, 08:48 PM
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#6
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I, Vettezuki
Join Date: Feb 2006
Posts: 14,754
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Quote:
Originally Posted by SeanPlunk
Paul said two other possibilities would be a bad coil pack, or clogged cats.
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The packs and cats came off fairly high mileage cars, so definitely a possibility. I wondered about that too. 
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10-04-2009, 06:40 AM
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#7
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Senior Member
Join Date: Jun 2009
Posts: 2,509
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It would be nice if you could get a CEL to help narrow things down to a single cylinder, or two. Also, Id check your fuel pressure. Maybe your not misfiring, maybe starving your engine of fuel and/or air? My GTO was running like crap without a CEL (bad fuel pump), so I went on the freeway and put the petal to the floor until I got a CEL. Granted mine is under warranty still, so that may be an iffy way to pop a CEL light for you.
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93 GMC Typhoon: new money pit/PITA. Now GT3788R powered.
Boost, because sometimes atmospheric pressure just isn't enough.
"If it has tit's or tires, you can be pretty sure your going to have problems with them..."
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10-04-2009, 07:08 AM
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#8
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Senior Member
Join Date: Jul 2008
Posts: 739
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I think I remember you saying you use an octane booster. Octane booster has been known to foul plugs. You might wanna pull your plugs and check them.
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HP numbers are good and all, but they are like asking someone how much they can bench. What difference does it make if I can still kick your ass?
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10-04-2009, 06:54 PM
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#9
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I, Vettezuki
Join Date: Feb 2006
Posts: 14,754
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Well, what do you think? Click on pic for gory details. I only pulled No. 1.
Plug wires themselves are pristine, are not in contact with exhaust and have heat shields to boot. These plugs only have only about 9,000 miles them from when the motor was put together. This includes tuning period which included many gnalry AFR passes. And yes, I run a small amount of Torco, Mach Fuel Accelerator.
These were not cheap plugs, AC Delco Iridium.
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10-04-2009, 06:57 PM
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#10
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Senior Member
Join Date: Jul 2008
Posts: 739
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I would bet that is your octane booster causing that.
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HP numbers are good and all, but they are like asking someone how much they can bench. What difference does it make if I can still kick your ass?
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