My evo starts with two dead cylinders 2 and 3 .


However when the battery negative is unplugged it runs fine.

I've spent 1000s trying to repair this. Thought it was objectors, cam sensor, crank sensor, aem ems unit gone bad.

However today I simply disconnected the negative on battery and all better.

 

Why not try a new battery first.

 

BAtt is new

Car only runs normal uf i unplug neg

 

Your just running off the alternator then, not good. How do you know cylinders 2 and 3 are dead? Are saying there is no spark in those two cylinders at all?

You probably are getting really high resistance in your ground system. Almost sounds like its easier on your electrical system to run off the alternator than to work its way through the ground at the battery. Get a multi meter and test your voltages and grounds. All this after verifying that your new battery is indeed good. Just cause its new doesnt mean it couldnt be faulty.

 

When your charging system is working correctly, the only time your car runs off the battery is during starting. After that your alt powers everything. You can disconnect your battery after is it started without any problems, assuming your charging system is working correctly.

However, something is definitely not working correctly. Check grounds and resistance on grounds. Have the battery and charging system checked out.

Correct me if Im wrong, but it sounds the spark or fuel injectors have a short to ground problem.

 

Disconnecting the battery while the car is running is not a great idea. While the alternator is powering the car, the battery still acts as a voltage stabilizer and the spikes an alternator can send out can affect/damage other sensitive electronics (sensors, ecm, etc). I agree with Tommi, check the volage differential between your battery neg post and where it grounds into the chassis.