TOP ISSUES I SEE WHEN TUNING

A lot of people think EFI tuners just push keys on a keyboard. It’s very rare, maybe 10% of the time when I’m tuning a vehicle and there isn’t some issue outside of the tune. It’s easy when starting out with EFI to blame the EFI system when often there are underlying issues to blame. As part of the “tuning” I spend a lot of my time troubleshooting one or more of the following:

Inadequate/wrong fuel pressure - The fuel pressure has to be rock solid and correct. The fuel pressure is specified in the ECU for EFI systems like Holley and Edelbrock. Factory systems look for a specific value. If you don’t provide what it’s looking for, all the fueling calculations will be off and it’s going to run terrible.

Low voltage - EFI needs clean, consistent power to run the ECU, fire injectors, power O2 sensor, and more. The alternator should be charging and the ECU should see over 13 volts. Gone are the days of “if it will crank it will start”. Before EFI, vehicles were very resilient to power and voltage issues. Running rough, failure to start, surging….all can be caused by low voltage. Make sure the alternator is charging and you have over 12 volts when cranking and the ECU reports 13+ when running.

Transmission issues - Mostly with automatic transmissions. If your transmission is not shifting correctly (up and down) it can put excessive loads on the engine. Heavy vehicles need to downshift to accelerate. Slipping transmissions make your engine feel weak.

Exhaust leaks - These throw off the o2 sensor and provide bad data to the ECU. Besides the MAP sensor, the o2 sensor is the next most important.

Bad or miscalibrated sensor - If a sensor is bad or you selected the wrong type it will throw off all the calculations in the ECU.

Incorrect ignition timing - Prior to crank triggers, you need to verify the EFI timing with a timing light, Many times on older vehicles this is an issue because the balancer ring might have slipped, the balancer was changed and the mark is in the wrong location, engine was rebuilt and timing pointer not set, etc. Most EFI companies such as Holley EFI refer to this as “Set Static Timing”. Correct timing is critical for all engine functions.

Hopefully this gives you some idea of the types of things that tuners can run into and why it’s a lot more work than just pressing a few keys!