If it is a fuel related issue you should check everything from the pump right down to the injectors. Make sure you are getting 1:1 fuel pressure if running the stock regulator.

I had gunk build up and damage my pump and fuel filter. Even after replacing those I had a weird idle issue where I'd come to a stop in traffic and the AFR would go lean in the 16-17:1 range for a few seconds before varying around stoich. Also some injectors use adapters that can build up deposits over time causing idle issues that cause owners to go nuts tracking down. Even if this isn't the issue it's a good idea to rule it out and make sure you're fuel system is operating as it should.

Some links on the forum that may be worth checking:
https://www.evolutionm.net/forums/6752164-post1.html
https://www.evolutionm.net/forums/11091285-post1.html

 

Was thinking about throwing some id1000's in.

 

Honestly, I'm surprised that you aren't running a stand-alone with the amount of money invested in your build. You should at least consider moving to a good stand-alone ECU like a Link G4+. I would also recommend going speed density. I hope you track down the culprit either way.

 

Definitely sounds like a fuel issue or tune.... I know others have already said these but these are the places where I would focus my trouble shooting in.

 

I reccomend going to SD... i had very simaler symptoms and once tuned on SD many cleared up.

 

Excellent will do. I actually did switch the pump from a 255 to the aero 340 but I will check again. I do get a similar idle irregularity like you're explaining.

 

more info is needed, in particular:

1) is the fuel pump hard wired for full time full voltage?

2) what are the idle and cruise trims?

3) what fpr?

 

My vote is exhaust leak near the front 02 sensor. You may not hear it, but there very well could be a leak which is causing the sensor to pick up varying readings.

 

Hello,

Can you let me know if it is the same thing on cold start or only when it warms up?

 

Pretty much all that seems like things a tuner can deal with. Whoever tuned it may have put a little rev hang in there.

 

Just make sure you don't have any leaks that sometimes causes it hang the throttle. I had a little leak by my throttle body and it was causing it to hang.

 

Pump is hard wired. Idle trim swings 12.0ish-17.1 ish as previously stated. Factory fpr, checked the diaphragm it doesn't seem to be leaking.

Checked it, it's all v band there're no leaks.

Cold start is odd as well it idles about 2k very rich then comes down once warmed up.

Please trust me massive tuning has went into the car street and dyno to address the issue. I wouldn't have posted on here if I did not already check.

Thanks everyone!

 

***Also everyone saying fuel pressure issue, I have a gauge on the way however, the car holds 29lbs of boost to redline at 11.7...

 

I suspect that it is a fuel pressure issue, at least for the wild AFR swings at idle. The hardwired pump is overrunning the return system at idle. It may not be obvious with a fuel pressure gauge unless you observe both at idle and the engine is under some load. The fuel pump power either needs to be returned to the stock configuration (low/high voltage circuit), or the siphon needs to be drilled out to ~2.5 mm diameter. The latter may not solve the idle AFR issue entirely, but it will help. Be sure to disconnect the battery after making either change, and depending on what was done to the tune, adjustments may be needed to the injector settings or the MAF scaling/compensation.

 

You have an aluminum block in a ct9a?