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Rod
11-02-2013, 05:37 PM
Carbed LS engine stumble problem at 5500RPM! any Ideas? driven and raced the car for 3 years and i just started about 4 weeks ago, I went to practice and right off the line the car hit 5500rpm and stumbled like a rev limiter,,,,here's what I have changed, and after each change a quick test run and the issue is the same

I thought maybe the MSD box, now new
bad Map sensor, now new
bad ground or power?, ran new wiring
bad coils?, 8 new ones
bad plug wires, now new
cam sensor faulty, new now
bad edelbrock carb, switched to a new holley
plugged fuel filters? I have 3 a post a pre and a carb filter, all 3 new now

ran out of ideas at that point, called MSD and they said alternator isn't charging? OK I'm game

now has a new alternator and an extra ground and a new charging wire and I have the same problem, just looking for any Ideas!!:hail:



any Ideas????

MrQuick
11-02-2013, 09:41 PM
I think you need new pedal covers. LOL

You gonna pull the covers tomorrow?

While you are in there check your rocker fulcrums.

reschke18
01-03-2014, 09:46 PM
Rod, did you ever figure this out?

Rod
01-03-2014, 11:13 PM
yes it seem the MSD box has a default, and for some reason after a year, it defaulted and wouldn't let the RPM chips override, and even stranger than that the new MSD box defaulted when we put it in so it had the same issue and also wouldn't let the RPM chips override either, so I hooked it up to an older laptop and reprogrammed the boxes, so MSD plugged the box in to see if there was a reason for the strange defaults, and make sure the files were not corrupted

Red67Mustang
01-05-2014, 10:53 AM
If you're still looking for possible causes (haven't fixed it yet) then I'd suggest you look at your fuel pressure. Sounds to me like your fuel pump could be failing and not able to keep up with fuel demand at 5500 RPM WOT.

Rod
01-05-2014, 12:35 PM
If you're still looking for possible causes (haven't fixed it yet) then I'd suggest you look at your fuel pressure. Sounds to me like your fuel pump could be failing and not able to keep up with fuel demand at 5500 RPM WOT.

it turned out it was the computer, funny you say fuel pump, I thought the same thing and I upgraded the fuel pump to the holley 12-700 HP good up to 900 Horsepower on Carb and holleys 12 -845 billet fuel pressure regulator with a return flow and a 30 amp relay kit, now I will never have doubts about fuel! :cool: if you look at my build thread I pulled my hair out and changed all kinds of gear, rocker arms, valve springs, intake gaskets, carbs, fuel lines and pumps, alternators, plugs, plug wires, coils(all 8), coil harnesses, it was crazy:seizure: