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engine will not rev above 6200 rpm
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Post engine will not rev above 6200 rpm 
new installation on Toyota 4age everything seems to work ok. Laptop displays advance, rpm and load but engine will not rev above 6200 rpm with or without load. Engine starts to cut out about 5800 rpm and will not exceed 6200 rpm at full throttle with no load, it acts like it is being limited via the ignition. 37 deg advance is still showing at 6200 rpm. Using dual 40 dcoe so should be plenty of fuel. Any ideas?

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Hi:

I would check the following:
* Coil pack. If not a new coil pack, it could be going bad where it only shows a problem under high RPM. But, usually this is high RPM + high load.
* Check what the ignition advance is doing when revving, using a timing light. Is the ignition advance suddenly retarding at high RPMs? if so, check the rev limiter settings in the Megajolt software.
* Check for sufficient supply current to the coil pack. what is the gauge of the wire and supply to the coil pack?
* Try switching out the EDIS module.

Let us know what you find out. Will watch for replies!


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Thanks for the list of things to check.
I checked the advance with timing light and it is still at full advance at 6200 rpm when the engine stops reving.
I changed the coil and the edis unit with the same result.
I closed the plug gap to .030 and this seemed to make the problem worse.
16g wire to coil, I did not check voltage.
I dont know how to check the rev limit settings, I only have the E version, no limiter installed.
Could it be the probe is not reading the 36-0 wheel? I'm using all Ford components.
Thanks
Tom

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Hi,

The Megajolt system has a built in soft rev limiter which activates by setting the ignition advance to zero, greatly reducing engine power. This can be used even if the hard rev limiter is not installed. You can see the current value in the software along with the other settings.

https://wiki.autosportlabs.com/MJLJ_V4_Operation_Guide#Rev_Limit_Setting

One thing is to check the gap on the trigger wheel and the rigidity of the bracket holding the sensor. If there are any vibration that cause the EDIS module to lose sync with the engine, then a symptom similar to this can occur.

Another test is to remove the Megajolt from the equation. If you unplug it, the EDIS module will hold the engine at 10 degrees BTDC in limp home mode. The power output will feel 'flat' and reduced, but it should rev smoothly throughout the range; there shouldn't be any sudden dips in power. If you do, then the problem is centered around the EDIS installation.

Thank you, will watch for your updates!


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I checked the soft rev limit and it was set at 8000, shift light 7500.
I checked the probe mount and checked the bolts for tightness.
The 36-0 wheel had weld cracking where the wheel fit onto the pulley so I rewelded it.
I test ran it with identical results, break up at 6200 and would not rev any higher.
I disconnected the MJ and used the edis only and it reved to 7000 but no higher.
I have a spare MJ for my next car to be upgraded and I installed it. Engine would rev to 7500 rather easily, I did not want to go higher than 7500.
I reinstalled the original MJ and the problem returned, 6200 max rpm attainable.
Tom

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Hi,

Thanks for the update. You might want to check and compare what the ignition advance is doing at those higher RPMs with the MJ plugged in and without. If you find anything wayward, you might want to check the current ignition map programmed into the Megajolt to see if it's doing anything with the timing around that range.

Also, if you know another fellow with a similar setup you can compare side by side to further diagnose.

Keep us posted!


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