LS6 Cobra
Possibly Valve Float..how far down does it dip when it lets off..
Thread Starter
TECH Apprentice
Joined: Jan 2002
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From: Gilbert, AZ
It is a factory crate GM ls6 motor so I doubt it is valve float. In nuetral is will rev to 6800 which is the limiter. Drive if you floor it it goes to about 5500rpm then feels like he let off until it coast to 3k then goes back to 5500 again.
And whip out your fuel pressure gauge and get a reading while driving it. TPIS sells one with an extra-long feed line, so you can tape it to the outside of the windshield in viewing position while testing.
edit to add: also scan your MAP KPa value, if starts decreasing in value as the RPMs climb you have a restriction in your induction tract.
Last edited by crainholio; Jul 21, 2011 at 09:55 PM.
If the car is new, with a new engine, I would venture to say the filter is probably new too. However the fuel pressure is a good thing to check.
How is the car tuned? Is it running a stock PCM tuned by HP tuners or something similar?
There could be any number of things that could cause the problem. Let us know when he figures it out.
How is the car tuned? Is it running a stock PCM tuned by HP tuners or something similar?
There could be any number of things that could cause the problem. Let us know when he figures it out.
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Verdad Gallardo Thread Starter
TECH Apprentice
Joined: Jan 2002
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From: Gilbert, AZ
It is a help me get it running good thread.
Fuel filter is new. Has good sized braided line all the way from the tank. Will check fuel pressure when I get a chance. We have a gauge long enough to do it. Doesn't feel like fuel pressure though. No missing, no knock, just shuts downs.
Fuel filter is new. Has good sized braided line all the way from the tank. Will check fuel pressure when I get a chance. We have a gauge long enough to do it. Doesn't feel like fuel pressure though. No missing, no knock, just shuts downs.
Really wish I could see the tune. Could be a lot of things. Check the ECT, MAP & RPM related timing tables, as well. Do you have a log of what is happening that can be printed & posted here. That would be helpful for us.
Thread Starter
TECH Apprentice
Joined: Jan 2002
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From: Gilbert, AZ
ECTs hover right ~180. All of those timing tables are factory ls6. I'll try to grab some logs but honestly they don't show anything wierd.
I thought EFI live could read HPT files?
I thought EFI live could read HPT files?
No, just tried & it sees unkown. Maybe, there's a newer version of EFI Live that you're referring to. Although, I've never heard of EFI Live having the ability to open HP Tuner files.
The issue is something simple. We just gotta find where it is in the tune.
It is a help me get it running good thread.
Fuel filter is new. Has good sized braided line all the way from the tank. Will check fuel pressure when I get a chance. We have a gauge long enough to do it. Doesn't feel like fuel pressure though. No missing, no knock, just shuts downs.
Fuel filter is new. Has good sized braided line all the way from the tank. Will check fuel pressure when I get a chance. We have a gauge long enough to do it. Doesn't feel like fuel pressure though. No missing, no knock, just shuts downs.
What fuel pump and tank does it have on it? could it be running out of fuel?
Edit- did nut read all the post to see that some have been saying could be fuel system related. If he fuel tank is not dumped or baffled depending on fuel level it could be sucking air and then cut out gas goes to pickup and can rev again only to do the same thing again.
Edit- did nut read all the post to see that some have been saying could be fuel system related. If he fuel tank is not dumped or baffled depending on fuel level it could be sucking air and then cut out gas goes to pickup and can rev again only to do the same thing again.
Unreal,
If not yet resolved, post it one section below in the "tuning section." You'll find a bunch of guys who can read the tune file & comment accordingly. You may get in a day information that could take a month, in this section 'cuz the tuning oriented people don't know about the problem unless they just happen to enter this thread.
If not yet resolved, post it one section below in the "tuning section." You'll find a bunch of guys who can read the tune file & comment accordingly. You may get in a day information that could take a month, in this section 'cuz the tuning oriented people don't know about the problem unless they just happen to enter this thread.
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lol. i thought the same. lol
both very good questions.
both very good questions.
Thread Starter
TECH Apprentice
Joined: Jan 2002
Posts: 366
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From: Gilbert, AZ
I was out of town for the weekend. Fuel pump is a walbro 255HP. Should support the power level just fine. I'll try to get some more data this week. Like I said, it is my friends car so I have to do it when he is available. He has a fuel pressure gauge but there is no where easy to tap it since the stock fuel rails don't have a port.
The factory fuel rail has a standard schraeder port on the front of the driver-side log, facing toward the front of the car, with a black screw-on cap covering it.
