RB25DET neo, randomly starts missfiring and causing lean idle

[alexdegnall]

Hello, I recently put my s13 back together about 7 months ago rb25det neo stock intake, stock exhaust manifold gtx3076r turbo front mount intercooler, running speed density 3.5bar map sensor from link, link iat sensor, r35 coil packs and prp 12 tooth crank and cam trigger kit. The issue im having is the car was tuned back in the beginning of the year possibly February and it ran very good and had no issues. Recently about a month or so ago when the weather warmed up I'm having a pretty big drivability issue. It seems that the afrs will randomly jump all over the place from super lean to super rich conditions. This seems to happen a lot worse when it is very hot out or raining with humidity. I replaced the iat and map sensor along with the plugs figuring maybe they went faulty, but the issue persisted. I just changed the tps out and recalibrated it thinking maybe the sensor was going bad as the log I took showed for a split second the TPS main % going to zero. I've checked everywhere for vacuum leaks, but haven't found anything. Soon I will try to rig up a way to put pressure into the system to see. Boost gauge reads almost -20psi of during idle. Any info or input would be great I'm not a tuner myself and have very limited knowledge when plugging into the laptop. I will attach the log of the short drive I took and maybe someone can chime in. Thanks, also the car was tuned in a closed loop system.lean afr misfire.llgx

[Adamw]

49 minutes ago, alexdegnall said:

Boost gauge reads almost -20psi of during idle.

That would be impossible, are you sure it is not inHg?  

I would confirm fuel pressure as the first step, most of the basics in the log look ok. Lambda doesnt mean a lot when there is a misfire so we cant put much weight on that.  I would also go to your GP output that is controlling the VTC cam and with the engine idling put the aux in test mode to confirm the VTC is actually working too.    

Probably not relevant to your current problem, but you log shows there is no acceleration enrichment working, so that probably needs to go back to the tuner to sort. 

With the engine off, does MAP read the same as BAP?

[alexdegnall]

My apologies you are correct it is inHG its reading about 18ish or so at idle currently. Fuel pressure is at 30psi. I will say I cannot remember off hand but I think I set fuel pressure to 40 maybe 45psi. I do recall a few weeks ago I noticed the jam nut came loose from the allen key set screw that adjusts fuel pressure. I suppose it could be quite possible the vibrations caused the jam nut to come loose and then the fuel pressure set screw lowered. I only tightened the jam nut back up if I increase the pressure slightly will it adversely affect the tune? Also I do recall seeing something in the computer saying vct inactive? Im decently computer smart, but not tuning smart and not very familiar with the layout of the program, if you could dumb it down for me a bit getting to that tab with GP output and putting it in aux test ill gladly hook my computer up and give it a go. Appreciate the response a ton 

[alexdegnall]

Trying to do this from my phone so not sure if it will come up properly here’s a saved file of the tune on the ecu if anyone wants to take a look if they see anything weird 

Degnalls rb25 tune.pclx

[koracing]

If your regulator has a hose connected to it and you're pulling 18-20inHg at idle - that's like -10psi from the base fuel pressure.  If you want to know what the base fuel pressure is at idle you would need to disconnect the vacuum hose from the regulator while it's running.

You don't currently have a fuel pressure sensor installed, and you're tuned in traditional mode, so any changes to fuel pressure will indeed affect your entire tune.

Your MAP sensor is listed in the software as a Link 3 Bar - but the MAP matches BAP when the file was saved so that seems accurate.  

There is no boost control set up in the software so you are using a separate boost controller?  How much boost are you running?  Your fuel table has entries up to about 17.5psi (220kpa), but your map limit is set to 20psi (241kpa).  Same with timing table.

VTC solenoid is set to Aux 6 output pin and controlled by GP Output 3 in the software.  Auxiliary Outputs --> GP output --> GP Output 3.  There should be an option to test once you select GP Output 3 and the window pops up - usually it's set to OFF and you will want to change that to ON to test, and then remember to turn it back off after testing.