Long story short...Since I've owned the car I've had some ESS error codes awhile back. I've cleaned and replaced the ESS about three times now. Codes have gone away (bought aftermarket ESS, worth noting.)


The car has had an issue with idling and throttle. When I would give it gas it would just hesitate. I would have to double tap the gas pedal to get going from a stop or else it would stall. Clutching into neutral it would die, or save itself and then "hunt" for idle. Cruising sometimes it would just start backfiring or misfiring.

It last occurred a year ago. I changed the plugs and coils, and ESS, and it went away. New fuel pump also. (given the mileage, they were all up for replacement.) (plugs replaced at one time, didn't help, ESS replaced separately, same thing, Coils done, problem went away.)

Now a few weeks ago, it started to have idle hunting issues again (only idle hunting issues.) It died on me once, but that was it. I cleaned and reset the NVRAM about four-five days ago. Still having the same issues. Today I have cleaned the maf, cleaned the throttle body, cleaned grounds. Cleaned the ESS, sprayed the hell out of every hose I could find to determine if there was a vac leak present (nothing.)

Only codes present are ones I have disabled in Versatuner (rear 02, as I am not running a cat, I'm running a test pipe.) As well as two for the secondary air injection system (pump unplugged.)

I'm at a loss honestly. The problem was gone for about a year. Now this idle hunting/bouncing has returned. Doubt its compression related, as it wouldn't have just stopped completely for an entire year if it was. I've included the data logs in versatuner format and .csv..If anyone could take a look and help me out, I would greatly appreciate it!

Logs are from a complete cold start.

 

Did you check the clutch position switch?

 

Can you add STFT/LTFT to the data logs?

 

I just put a BHR clutch pedal on the car a few days ago. In the process of, I had to transfer the switches over. Both switches are only getting contact/no contact when they should be.

 

Sure thing. I had a feeling I should have added those prior. I'll go do a cold startup log now, seeing as I haven't started it for the day. back in half an hour ish.

 

Here we go. I made sure I included the STFT & LTFT in the logs this time. It was logged from a cold start as well. At two points towards the end of the log, free revved it, gave it time to settle down, then did so again, so it would better log the issues i'm experiencing. Really appreciate the help on this one!

 

Whoa. Your LTFT is -18%, but your STFT is maxed out at +25% and the observed AFR is lean. I have never seen this. When you give it a blip, STFT goes to 0 LTFT goes positive... then it settles back to negative LTFT and 0 STFT.

And the whole time you're running lean, but your airflow (once it settles) seems OK, 5.6g/sec.

Actually it seems the surging behavior stops when STFT goes positive. It's about a minute in, perhaps that's when the 02 sensor has warmed up and it goes to closed loop.

Can you pull reset NVRAM, pull the battery and let this thing learn to idle from cold again without touching it? I don't know enough about how LTFT is calculated, specifically, but it doesn't make sense to me that it's would pull fuel via LTFT, then add it via STFT, and still not be able to reach proper AFR. Possible one of your sensors is lying - MAF or O2.. but let's just try that software reset first.

Also since you have VersaTuner, how confident are you the tune is well done?

 

It's the Versatuner base installation. Its essentially the exact same tune as the factory, but it allows for customizations. The only thing I've done is disable two codes. One for the downstream 02 sensor circuit being low (I have no cat and the plug is kind of messed up.) and the other for the secondary air injection system (air pump unplugged.)

This log was taken after the NVRAM was reset a few days ago. I can reset it again if need be, but After resetting it, and all the drive cycles..it hasn't fixed itself.

Maybe the intermotor ESS I have on there? But that still wouldn't explain why the problem would go away for about a year then return...or would it?

Edit: maf has been cleaned as of yesterday. hell, I even put a tiny bit of gasket sealant around the mount on the intake tube to rule out any vac leaks.

 

Who knows. Maybe it's the wiring to the ESS. I think you'll need to start eliminating variables one by one. Do you have another ESS you can swap in? Another MAF? Can you uninstall the VersaTuner tune and go back to stock temporarily? What other mods have been made?

 

When did you install VersaTuner?
What else have you done to the car immediately before this started. Usually when you fix something and it's OK for a year and you get a problem it's something else. A bad ESS will not usually cause just a 1-2 minute problem at cold start....

First thing I would do is go back to a known good map...so in your case I would go back to stock....and then wait a few drive cycles for the ECU to get itself straightened out. If it still does the same thing you know it isn't the map.

 

I installed VersaTuner about three weeks ago I want to say. The car showed signs of this shortly before It was installed on the car, as well as a year or so ago like I mentioned. I was told that only installing Versatuner on the car changes nothing, it simply allows you to flash/edit tunes, disable DTC's, etc. The only mod the car has is a megan racing midpipe, which has been on it for quite some time (over a year and a half at least.)

It behaves this way if its warm, cold, etc (in terms of the idle surging.) Especially if its stable and i blip the throttle, or clutch into neutral when cruising to a stop.

Driving there are no noticeable issues, with the exception of one time I did a WOT pull two weeks ago and the car flashed a misfire and just stopped dead in its tracks briefly.

 

Swapped in another ESS (Mazda OEM) and MAF, cleared the NVRAM. Ill give it a few drive cycles to see if it learns its bearings.

 

That couldn't possibly be related...

How's your fuel pump?

 

Funny you mention that...I did just have the fuel pump recall done at the dealer. They had to order an entire new assembly all together.

 

Well, the problem has since gone away. It hasn't resurfaced yet.

Im leaning towards the possibility that those aftermarket eccentric shaft sensors just do not vibe well with my car, the one on there now is mazda OEM.
OEM ESS on the right, intermotor on the left. May be nothing, but the size of the magnet itself on the OEM is larger than the aftermarket counterpart.

 

swap the MAF back to make sure 😎

 

Indeed. Working fine still. Maybe my PCM is just picky. Versatune had to add support for it before it would install onto the car.

I figured if this was more of a widespread problem it'd be documented. Im chalking it up to my PCM just being picky.

 

That's odd. What ECU do you have?

 

Per versatuner, its N3M1EK00013H6020.

 

Just checking in, No idle issues whatsoever to this date with the OEM ESS installed. Maybe my car/PCM is just picky like I mentioned previously.