LS7 Low RPM Miss
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Joined: Oct 2015
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From: Maryland
LS7 Low RPM Miss I have an LS7 with PRC 285 heads, MSD atomic intake, NW 103 throttle body, kooks 2in headers, 232/246 .635/.635 cam. It has slowly developed a miss or something under load below or at 2000rpm. Its random, and enough to jerk the car while driving. I notice it most in 6th gear. I have replaced the spark plugs (none looked bad), spark plug wires (i also insulated the new ones), and done an oil change looking for metal ( i found none). I checked the grounds on the harness and the plugs. I haven't found anything glaring. There are no codes, no flashing CEL, no nothing. Just the miss. It doesn't do it under hard acceleration, it still has good power. Other than the random miss while cruising, nothing seems to have changed. So far as I can tell, it doesn't do it cold. What would you start looking at first?
I have an LS7 with PRC 285 heads, MSD atomic intake, NW 103 throttle body, kooks 2in headers, 232/246 .635/.635 cam. It has slowly developed a miss or something under load below or at 2000rpm. Its random, and enough to jerk the car while driving. I notice it most in 6th gear. I have replaced the spark plugs (none looked bad), spark plug wires (i also insulated the new ones), and done an oil change looking for metal ( i found none). I checked the grounds on the harness and the plugs. I haven't found anything glaring. There are no codes, no flashing CEL, no nothing. Just the miss. It doesn't do it under hard acceleration, it still has good power. Other than the random miss while cruising, nothing seems to have changed. So far as I can tell, it doesn't do it cold. What would you start looking at first?
i just had similar issue and mine turned out to be a bad coil pack on cylinder 4. Replaced that coil an issue resolved. But i used HPTuners VCMscanner tool an logged my misfires while cruising and that pointed me at which cylinder.
i did all the samw things you did first as well which didnt help until i got a new coil pack. An my bad coil wasnt completely dead it was just weak.
Thread Starter
On The Tree
Joined: Oct 2015
Posts: 113
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From: Maryland
if you have access to any type of scan tool or scanning software to monitor cylinder misfires. Watch the scanner when you feel the miss an this will give an idea at which cylinder at least your problem might be in or if its truly a miss at all.
i just had similar issue and mine turned out to be a bad coil pack on cylinder 4. Replaced that coil an issue resolved. But i used HPTuners VCMscanner tool an logged my misfires while cruising and that pointed me at which cylinder.
i did all the samw things you did first as well which didnt help until i got a new coil pack. An my bad coil wasnt completely dead it was just weak.
i just had similar issue and mine turned out to be a bad coil pack on cylinder 4. Replaced that coil an issue resolved. But i used HPTuners VCMscanner tool an logged my misfires while cruising and that pointed me at which cylinder.
i did all the samw things you did first as well which didnt help until i got a new coil pack. An my bad coil wasnt completely dead it was just weak.
I have HPtuners and took a log of me going to work with it in VCM. I haven't had time to look through it yet. This weekend I'll check it.
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On The Tree
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From: Maryland
I went through my logs and there were 0 misfires reported on any cylinders. Even though the lurch has gotten much worse. I'm not sure what to do at this point. The only thing I can notice is a jitter in the spark table, ST fuel trim, and MAP when it does it. But that might just be because its being affected by the slight drop in RPM. I have no idea now. How can I check the coils? Also, its really only doing it once its warmed up, and I don't mean just the coolant, the oil too. Could this be a dead lifter and I'm just not hearing it yet? It had copper in the last oil change, quite a bit actually. But its still got killer oil pressure. I'm no sure where to turn at this point other than to start taking it apart and poking around.
I went through my logs and there were 0 misfires reported on any cylinders. Even though the lurch has gotten much worse. I'm not sure what to do at this point. The only thing I can notice is a jitter in the spark table, ST fuel trim, and MAP when it does it. But that might just be because its being affected by the slight drop in RPM. I have no idea now. How can I check the coils? Also, its really only doing it once its warmed up, and I don't mean just the coolant, the oil too. Could this be a dead lifter and I'm just not hearing it yet? It had copper in the last oil change, quite a bit actually. But its still got killer oil pressure. I'm no sure where to turn at this point other than to start taking it apart and poking around.
Chris
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Thread Starter
On The Tree
Joined: Oct 2015
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From: Maryland
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