Weird idle/Rev hang
 

I purchased this Miata with no tuning knowledge, and I have been trying to make it run better on my own and learn the software. But I'm still having weird idle issues even after closed-loop. It used to idle and use the target rpm. But I am not exactly sure what happened, it's no longer targeting the rpm . It also started to rev hang after I switched to closed-loop. Didn't do that in open-loop. So I'm sure it's something in the Closed-loop settings. Also If ya'll see anything off or unusual please point them out. I been in a circle these past few months, :idea::facepalm:


https://cimg9.ibsrv.net/gimg/www.mia...af161667b5.png

Just needs to be tuned. Try this one, it won't be perfect but a step in the right direction... should fix the idle hang and bring your target down to a more reasonable 850 RPM.

If you want help tuning it, PM me :cool:

Yea. It idles but it's still rev hanging.

Post a log please.

Sorry, I was up at 4 in the morning data logging. I forgot which one I wanted to use. But. All of these 3 data logs should have rev hang.

Your idle valve was set to inverted, meaning 100%=closed, instead of the typical open. Not 100% sure what this is going to do with the rest of your settings, so just load this tune, log it again, and we'll go from there.

Edit: this isn't going to affect your idle, but your MAT sensor is doing something weird. Constantly spiking to ~35*f, then slowly falling back to 0. Might want to get that fixed.

Oh, i don't have a MAT yet. I have a MAF but it's unplugged. I really want to install an IAT soon.

I switched to "invert to normal" on a tune file a tuner shop tuned for me. I was just playing and comparing tunes. (Tune is basically the same as my current one). It started to rev up really high, I even tried to drive it like that to datalog but in between shifts it would just rev up. Also I just remembered, It did the exact same thing on my current tune. I forgot. I did it super late at night. OOps sorry. :crx:

BUT here's the datalog

It is impossible to diagnosis a problem with if you're not providing the tune used when the datalog was recorded.

In the datalog "inverted", your idle valve started at 30% (fairly high), and eventually went up to 40%, so if your RPM followed, then it's behaving properly. The tune I attached above had a minimum idle duty of 18% IIRC, again this log never went below 30.

My bad, I forgot i did that when playing with tunes. Sorry.
I changed it back to 18.0 for idle valve closed duty.

Nice catch @Curly. Valve pegging 18% DC, still lounging around 1100 RPM. Throttle plate may be cracked open slightly due to throttle stop adjustment/junk built up in the throttle bore/cable too tight/etc.

Not too long ago, I did clean the throttle body and intake system. Also whenever I first got the car the very first thing I did was adjust the throttle cable because there was a lot of dead pedal play. But I'll loosen it a little and see if that changes anything!

Yeah, but at 1100rpm he's idling at 4.5*, later in the log idle advance correction isn't on, and he's at 2500.

I would also suspect either a throttle cable that's too tight or leak in the system.

OP, does your TPS reading smoothly follow pedal movement? You can check this with engine off.

I loosened the throttle cable a little and it didn’t change anything but, I was searching for vacuum leaks with carburetor cleaner and i found 4 vacuum leaks. All 4 bottom seals for the injectors leak air. Or at least i think so. Every time i spray on the bottom seal, it makes the engine shake and stumble.

And yes, the TPS does read smoothly.

Sounds like you have the cat by the tail :likecat:

Fix your leaks and give it another shot.

We’re so back guys. So the new seals worked. And i had some flow-force 640cc injectors that i been wanting to install. New o-rings, new injectors, new settings loaded into tuner studio. No more rev hangs. It now idles lower and it actually reaches the target rpm. It all worked out in the end.
:party:

Thank you Rracer, and Curly.