I’ve been having a weird idle rpm oscillation issue with my turbo NB2 that primarily pops up when it’s Florida cold outside (below 70) and after a cold start. It’s happened after sitting for a couple of hours but it’s much more rare. I don't recall this happening at any point during the summer.

The oscillation seems to mostly occur when the water temp hits about 140 and continues for a little while after it’s warmed up completely.

In the attached log you can see the idle issue clearly at 250s and 410s.

Playing with turning the AC on and off sometimes seems to help. Turning the car off and then back on seems to fix it most of the time but that’s not exactly the most reasonable solution in traffic.

With the advice of my tuner, I tried adjusting AFR/EGO Control to be active above 1700 rpm instead of 700. That didn’t seem to have any affect on the issue so I changed it back. He’s a little hard to get ahold of so I haven’t really been able to get more out of him.

Here’s the tune:
https://drive.google.com/open?id=1z0...C5qqH6OHTDhNAK

Here’s a log:
https://drive.google.com/open?id=0B_...RxR2xoTjhRMWVJ

Any help would be appreciated. Let me know if you guys need more info.

 

Did you ever get this figured out? Sounds to me like your WUE is off a bit. If it happens at the same coolant temp everytime, maybe try upping it. EGO might be trying to bring it to the right AFR which causes it to go rich where it should be but the WUE is then making it too lean and then osscilating because they are going back and forth. I'm pretty much a beginner when it comes to tuning so take this with a grain of salt. I believe that's what I did to fix mine. I can't look at the tune or log, they are a google drive which is messing with my setup. Idle being stable once its warmed up makes me think it's WUE, if it was right after starting it would make me think ASE. EGO just makes corrections it won't keep it where you want unless it's pretty much there as far as I understand, but once again grain of salt.

 

I just updated the original post with non-google drive links to the files. I don't remember why I thought it was a good idea at the time to upload them that way.

I haven't made any progress on the issue. I talked to my mechanic about it the other day when I was getting an A/C problem looked at and he was under the impression that the idle air control valve could be going bad. He claims his drift 240sx does a similar thing due to him somehow bypassing the IACV all together. I don't know how or why you'd want to do that but that's how his 240 is setup.

 

I looked at the long and that **** is everywhere lol. I doubt it would be your IAC valve but I don't know. Can you upload your tune again? I can't see it at all. It is saved as some weird file. Just open your tune and save as, then upload that to here.

 

Here's the tune fresh off my laptop, hopefully it loads better for you this time.

 

Man it is just not letting me open it. Keep getting some Http 500 error, when I get a chance I'll try a different computer. Hopefully someone else can see it and chimes in soon

 

PM me your email and I'll try sending it directly if you'd like.

 

It looks like the EGO correction chasing its tail; try setting a higher minimum RPM and see if that smooths this out. The fueling also seems to be a bit rich at that point.

 

I tried changing it to 1700 rpm earlier on the advice of my tuner. It didn't seem to make a difference at all with the oscillation. At 256s in this log you can see the oscillation.

 

OK, we've taken one issue off the table - the injector pulse width is now a bit steadier. I would also try flattening out the spark advance table in the same region as that seems to be contributing a bit.

 

Matt, think something could be off with Idle VE during his warm-up? It is set to come on at 140 Coolant temp and that is right when he said his issue started happening. I'm very curious as to what is causing this, have you gotten it sorted yet? Would love to learn more about tuning and what is causing this.