cant push past 3000 rpm

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dirt wagon

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I've got a MP electronic ignition with the orange box on my stroker small block. When laying into in it gets to about 3000 rpm and starts sputtering and wont get any higher. Its as if there is a rev limiter on it. Any clues? A friend suggested I check the ground on the box but im pretty sure its ok. Thanks.
 
mopars love grounds try what your buddy stated. Do you have one from body to motor ?
 
I bet we would need more information:

When did this issue start?

Is this a new engine?

Is the carb in proper working order?

Do you have a good fuel line, filter and pump all clean and working well?

Did you make a change recently and now the issue has come to light?

First verify of course that your plugs, plug wires and distributor cap n rotor are in great condition. If you have problems with any of those you could get your symptoms. If all that is good, it sounds like a bad ECU (swap in the new stock one) or if that does not fix the issue it may be low power to coil or to ECU.

I would get a new stock ECU box for testing, then save it for a backup and leave in the trunk. Orange boxes have a reputation for being failure prone.


Check ground on ECU back to body of car where it is mounted. It needs to be sanded shiny metal on the ECU backside where the bolt holes are and the place where it contacts the car body. Next start checking voltage at the Coil + side while someone revs it up to 2K..Coil should have 7-9 volts (someone pls correct me on this if not correct) if you still have your stock ballast in place.

Next check voltage to ECU while revving it up to 2K. The MP ECU will only have (need) a 12V source and it should be near 14V when it engine revved up to 2K. .

Check reluctor gap in distributor.

I have had approx 3k rpm missfires causing popping out the tail pipe b/c plugs went bad after running down the road in a rain storm sucking in water into the engine thru the hood scoop (I was young and didnt care). Several days later the plugs simply started to fail and the engine sputttered under mild load until I swapped all the plugs.


Otherwise I would suspect that timing is drastically too high or erratic due to improper timing curve or loose parts in the distributor. Check out internal distributor parts to be sure they are not flopping. Put a timing light on and see what total is at 3K. Try disconnecting vacuum advance if it is connected (just as a test to lower the total timing) .
 
X2 on grounds!

Ground it real good to the battery/engine block. Easiest first step. My orange box was grounded to the firewall with a small wire...not enough...good luck!
 
Could be a bad ground, but when the boxes burn out you will have these same symptoms. They seem to burn out quite regularly these days. Amazing how the quality has just gone right down the tubes.
 
I do agree that you should have factory grounds in place and be damd sure they are clean connection points. At minimum Batt to engine, batt to car frame. Clean battery posts, battery terminals and ground connection points and re-connect. Gotta be sure they are not loose or corroded. Both the surface of the ground wire and the place where the ground makes contact to the block or frame must be shiny metal and tight. You probably have high humidity down there so connections may be your issue.
 
..is this the Mopar Performance Mallory Distributor?
if yes,remove the extra light pink springs and recurve it to advance slower.
... all in around 2800
 
OP: Your symptoms say this happens when 'laying into it'. Have you tried going past 3000 rpm with the car at, say, half throttle? If OK to past 3000 rpm, with half throttle or some level of light throttle, then look at the fuel system and carb. You may be chasing your tail 'til you try this to see what happens..
 
Orange boxes burn up if you push the rpm's over 5500 as that is all they were designed for. I burnt up 3 before finding this fact out

Step up to the chrome mopar box
 
Where do you make contact on the ecu when checking for voltage? I checked at the round metal surfaced thing and only had 5 or so volts at 2000 rpms.
 
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