Save Preloader image


Magneti Marelli Tuning Issues

Magneti Marelli Tuning Issues

When tuning our product on Harley Davidson motorcycles with Magneti Marelli EFI system, the dual throat EFI used from 1995 to 2001, there is a possibility of coming across mechanical and/or sensor issues. These pre-existing issues can confuse the tuning procedure and prevent you from achieving the best results.

If our base settings seem way off, or if following our basic adjustment sequence (#4) does not react as we suggest and result in a smoother fast idle, then you should look into the following;

  1. In all the following tests and tuning, it is very important to ensure you are working on a fully warm engine. A minimum of 15 minutes of riding the bike and then a 2-3 minute idle is recommended.
  2. make sure the bike idles at 1000 to 1050 rpm. NO exceptions. Remove the aircleaner to adjust the idle and ensure the high idle linkage is not engaged. See your shop manual. Once you have made the adjustment, re-install the aircleaner and double check the rpm.
  3. check for intake air leaks. Spray an aerosol carb cleaner around the manifold to cylinder head joints  while the engine is idling. If the idle changes, you will need to fix the leak before proceeding.
  4. turn the bike off, then cycle the ignition on and off ten times, allowing the fuel pump to start and run until it stops each time.
  5. turn the bike off, pull the two fuses under the right side cover for 15 minutes. (or disconnect the ground cable from the battery). Now replace the fuses.
  6. now start the bike and re-attempt the basic adjustment as per #4 in our instructions. If there is still no improvement, disconnect our unit.
  7. remove the aircleaner assembly and access the TPS (throttle position sensor) on the left side of the intake manifold. Turn on the ignition, and using a voltmeter, check the reading between ground and the gray/purple wire. It should read 0.47 volts. If it doesn’t, loosen the torq screws holding the TPS sensor and carefully turn it until it does. Tighten the screws and recheck your voltage.
  8. remove the fuses again, or disconnect the ground cable for 15 minutes, hookup our unit and try tuning the green fuel pot as per instructions again.
  9. If you idle has changed, remove the air cleaner, reset the idle to 1000 to 1050 again, pull the fuses again for 15 minutes and tune our product again.

Another common problem we see is a failed cylinder head temp sensor. The problems arising from this sensor failure are erratic driveability, the problem is there one day but not the next, etc. Also erratic backfiring and inconsistent fuel economy, are signs of this sensor failing.