I'll jump right into my issue. I have the Apex'i NEO tuning my DE-K Swap with stock 99 ecu and harness. I usually run 10-15 points lean from 1000-6000 rpms at 12.5-13 a/f ratio (above 50% throttle). Every once in a while my tune will jump and Ill be running 16-18 a/f ratio above and below 50% throttle. I thought this might be my exhaust leak causing this, but I've replaced all gaskets. When it jumps its always consistent in how much it jumps, so i have tune settings on a piece of paper to tune from lean to rich and back.

No codes.

Any help?

 

Have you checked for any vacuum leaks? Unmetered air can mess with your tune.

 

All new lines with swap, but ill double check.

 

I could not find any leaks, and it happened again last night. Any other suggestions?

 

colin, it could be the colder weather. my tune def. changes with colder air because the air is more dense when its cold so being more compact it will lean out a bit.

 

Yeah I know the cold definitely lets the motor perform better, but this is a drastic change. Running from 12-13.5 to 18 and up.

 

If AFR is tuned according to MAF voltage, then the cold air wont affect the tune because the MAF will compensate for the denser air. But if your tune is based on throttle position, then ya it will change with temperature.

To the OP, have you checked your fuel injectors or fuel pump.. Maybe you have an intermittent problem with an injector/injectors or pump where the injector cuts out or the injectors are partially blocked and is leaning out the mixture or the pump is on its way out and you have intermittent fuel pressure drop.


Also check to see that MAF voltage rises in a linear fashion as RPM rises and check your TPS for proper calibration and that voltage rises without dips and is also linear according to the throttle position. This most likely isnt your issue but never hurts to check the simple stuff first.

 

 

Good info, Ill look into that, and report back.


related to the issue

 

I was just giving you a free bump.