Sputters under load
 

428, carb, MSD 6014. My car will sputter under load at about 3000 and above.
We got to go 6.60's in 8th and always noticed a small miss or what we thought of a miss when making a pass. It progressively got worse where now it will start and idle fine, rev good and even drive all day without issue. Get into the throttle and it sputters and sometimes spits through the carb. Turn it off and starts up and runs fine again as long as you don't go into the throttle hard

Now it's been over a month and trying different things.
Replaced crank sensor and thought it fixed it for about a few days so maybe it was a fluke.
Swapped out or replaced:
Coils and harness
Cam sensor
2nd Carb 1st was E85 then to gas carb, neither was lean at all. have AF gauge
New plugs, new wires.
MSD box
new harness 24x to 1x timing gear front. had it spliced before.
Ran power and ground directly to battery. MSD told us to try that. it bypasses relay and key start to check box.
Crank sensors (3 of them) 1 AC Delco
Fuel pressure rock steady 7lbs
new ground cable
moved MSD coil grounds on different locations
Cut the tach wire and the pink wire from MSD harness to make sure it wasn't that.

Now also checked valve springs and nothing broken, I've read bad reluctor wheels but would the car idle fine and start good, even rev up.
any ideas would be appreciated.

Check your trans? My car has been acting weird and I think it's the converter, in a burn out when the tires spin it's fine, but now it's really slow coming up on the trans and feels like something is holding it back

Check for vacuum leaks.

This sort of thing is almost always AFR related so weird that your AFR gauge is reading good. Is this a data logger AFR or are you trying to eyeball the gauge while running?

Also how do you know the fuel pressure stays good under full throttle? A sticky float could cause this but again should show up on a recorded AFR

yep we thought it was fuel related, checked pressure and its 7lbs rock steady. even opened line up to bucket and saw how much it flowed 1 gallon. It's running rich on E85 brand new carb, so then we emptied tank and tried gas carb and exact same results. Floats have been rechecked and checked. When your rear jet on E85 is over 100, you hope it's not lean lol
The AF is a gauge and have had people in the car to watch certain things and my laptop to watch other things lol.
Idles rock steady and at about 800 so doubt it's a leak. Carb has no vac fittings on it and intake only has fitting to go to Map on MSD box and we capped that off to to try. Holley intake we Put Felpro paper gasket instead of the O rings as we did have an issue in the beginning with the 0 rings but not related to this. We sprayed the intake for leaks too.
It's like it's hitting a wall at around 3000 rpm. sputters, then you restart and drive it back no issues. You can also free rev it pretty good.

Pull your float bowls off and see if you have jelly in them. If you do. Clean them with carb cleaner. Make sure you pull the metering blocks off and clean them too. Carb cleaner melts it off.

He tried 2 different carbs along with different fuel, I doubt that's the issue.

What really worries me is that you say it got progressively worse and you have already changed everything ignition and fuel related and it does the same thing. Have you tried pulling the plugs right after it sputters to see if it's loading up or going lean? What plug gap?

PS Ignition/fuel (Tune) problems tend to show up only under load because that's where it's seeing it's highest cylinder pressure. As pressure increases so does the need for a strong spark to get it ignited at the right time. So it may idle and rev fine with no load but fall on it's face under load.

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yep actually 3 carbs, lol one E85 and then 2 gas. even tried to run 2 pumps and 1 pump. I have a triple hat system for fuel. had 7's and then went to 6's on the plugs. on E85 we where a little rich and on gas I probably could fine tune it with maybe 1 or 2 jet sizes bigger. plug gap we have it down to 28, so it's ready for nitrous if I got that far.
I figured if it had a bad crank signal it would show up on my MSD box software when I look at it.

well I'm going to pull the heads off, today we pulled the plugs out to just check them again and 1 doesn't look like the others! always that 1 guy.
when this first started we pulled the Br7's and they looked perfect but hard to tell with E85, so we put TR6, and ran them but never gott past 3200 to 3600 rpm breaks up. Played with timing all over the board so hard to tell if it's part of the problem or a new problem we created on testing everything hard.

Not sure how well it shows up in the pics but one plug, the electrode is more of a rust color? or got hot? where the soot mark stops there are bright speckled pieces. about 3 of them across the electrode like you threw them at an angle. we almost missed it but kept looking with bright lights and magnifier.

https://cimg9.ibsrv.net/gimg/ls1tech...8f3af721f.jpeg

https://cimg0.ibsrv.net/gimg/ls1tech...a5bd463c1.jpeg

https://cimg1.ibsrv.net/gimg/ls1tech...6b1bcdd40.jpeg

https://cimg2.ibsrv.net/gimg/ls1tech...bc6b3c99c.jpeg

https://cimg3.ibsrv.net/gimg/ls1tech...97f969883.jpeg

you can see a little damage at the base of the electrode

https://cimg4.ibsrv.net/gimg/ls1tech...c3c603ddb.jpeg

right at the soot line are the specs.

going to check the heads good, I know on my 6.0 I melted 2 electrodes off from nitrous and the car still went in the 6's and still drove good lol. My old 6.0 was durable. This 428 not so much :)

Have you checked battery voltage to the 6014 on the data logs.
What is the current software version on the 6014.
What version of the MSD view are you running.
There have been 3 software upgrades for the 6014 in the last year.
Two of them I bought it to their MSD attention and they corrected it quickly but the bad part about the upgrades it changes the box back to stock and will need to be reprogrammed.
The problems that I have found was with the ICTiming not saving to the box you could make changes and save but when you unplug the box from your laptop and then reconnect the changes were not there.
The second problem was with the Step retard minimum RPM setting the same thing happened as with the ICT.

One other thing is to check is the crankshaft reluctor I know of a 24x reluctor that was not true on this stroker crank causing the engine to bust out bad at higher rpm.

yes the MSD has the latest software and we wired it directly to the battery and ground, bypassing the relay. per MSD instructions from their engineering dept. to just test box. luckily my friend has the same box so I borrowed that one too. we where wondering about the wheel on the crank but the engneer told it us it would show a fault.
I disconnected all the extra wires, step, tach and retard.
I have 4.3.28 says current version.
what's bad is it did work perfect, car went 6.6 in 8th and the miss kept getting worse and worse. I could drive it thru the miss ( was only mid range miss) but now it's like it just quits at about 3500 rpm. sputters back down and I feather the throttle to keep it running. Turn key off and restart car and acts like nothing happened. free revs and idles nice. give it load and sputters again.
voltage was around 13.2 range

Was this problem resolved??? Have the exact same issue.

Yep we found out, trashe'd the motor and sold it lol. Hate to say it but the crank wiped the thrust bearing. Pushed the crank forward so much it caused the crank sensor not to pickup the reluctor wheel signal. We think it might have been caused by the powerglide. Have a new 403 going in now.

My buddy pushed and pulled on the harmonic balancer and saw it had to much movement and then realized we had to take it apart to see.

Hate to hear that..Thanks for the reply!

Seems like I've run into the same problem. First time out, the burn out was fine, took it up to about 5 or 6,000 rpm, then down track every time I cracked the throttle open is was nothing but miss firing. Why do you think the trans did it? Did you check how much play was between the converter and the flex plate? I did check mine and set it per the recommendations. I did tack weld the reluctor wheel to the crank (straight up junkyard short block), I hope a didn't screw something up. Probably the first thing I need to do is replace the cam and crank sensors. My fuel system is untouched from an old engine, so I feel that is good.

So the data log didn't show any sensor faults?

Was it due to the converter ballooning ?
or
Was it maybe converter snout not seated right ?

Did you find the problem?
 

I had the same issue, ran perfect, fell on its face at 3500 rpm no matter what I changed
Tried new 6014 box, fuel system, plug wires, grounds, timing .... Everything !!

Then grabbing at straws I removed the new msd coils, and threw on some old ones of a stock engine in the shop... And now it runs perfectly, all the way to 7000 under load, tires on fire