Siks6

Have you ever had an open circuit to your AFR gauge when the car was running?

If so, and fixing that said open, have you noticed how the AFR reads funny and cold starts suck?


Well, let me tell you a funny story. The two questions above are legit questions as this has happened to me. Couple of years ago (September of 2022), moved back to Colorado, had my car retuned to altitude. I will explain my set up shortly. Once I was tuned, the car ran well, real well. Cold starts weren't a hassle, it was a genuinely happy car. One day before going to a cars and coffee, I was warming up since I was needing to get ready, found that my AFR gauge suddenly stopped working, car was smelling of fuel. I shut off the vehicle, inspected everything. Found there was an open circuit in my AFR gauge itself, specifically, a loose ground. Fixed the issue. Car ran fine when it was warmed up....

Here is where things become more noticeable. When it's warm, it is fine, once I tip in or blip the throttle, the readings lean within about 1 or 5 milliseconds, but goes back to where it goes. By sound it doesn't seem like it is knocking when doing so, feels just fine. idle readings are fine, full send feels decent overall. Once the car fully cooled off, that is where it started to make me panic a bit. I would have to crank it, seems like it was seriously leaning out, almost knocking. But once It finally caught on, it'll start to warm up, but I would have to be on throttle or watch my AFR readings. Once it warmed up, it was fine.

Contacted the tuner, they stated that I would need to get my tune checked whenever possible. All of 2023 I was doing nothing but rebuilding my whole suspension. So with that, and having to take care of my family, and a job change, I had no time to get back onto the rollers. April of '24, I finally get onto the rollers. The tuner claims that I have made power (to which I lost power due to humidity, temperature, all the fluctuations you typically see). I told them exactly what happened, they said the car ran real well. Hard pulls and the car wanted more.

Okay... Found they didn't even check any settings, the tune itself, just sent onto rollers and called it good. Okay. Time to datalog, something I should have done from the start. Showed them the readings. Then they requested for me to come in ASAP to fix something. Okay. Couple of weeks later, get back in, then they claimed the AFR gauge is no good, to which I can understand from their point of view. So I put in a new AFR gauge, wiring harnesses, wideband, everything. After a couple of days of wondering what the hell, had to fix a setting in the gauge and the car runs again..... like what it did after I originally lost my ground. Sent them a very recent datalog and they have yet gotten back to me.

The car:

1999 NB1.
BP4W
Jenvey ITBs
stock injectors relocated
Fuelab FPR set at 60 PSI
OEM pump
Flyin Miata Full exhaust system
Racing Beat headers
Flyin Miata intake cam gear (one tick advance)
Fidanza exhaust cam gear (one tick me)
Supermiata coolant reroute
Mazdaspeed intake camshaft
No PS or AC
Competition Clutch 5.5 lb flywheel and twin disc clutch

What has been replaced:
AEM AFR gauge, wideband three times, spark plugs, oil, fuel, literally any maintenance stuff that could affect the car.

One thing I have noticed when datalogging: Once warmed up, my ignition timing stays from -2.5 degrees to 0. revving past 2K it gets up to and stays at 40 degrees. Full send seems fine around 32.

So once again... Have any of you guys ever lost a ground or had an open circuit in your AFR gauge when the car was running or when turning it on? What did you do to fix this?

I can provide datalog if needed.

Thank you for reading this and I hope I can finally get this resolved.

redursidae

A data log and your tune would be helpful to verify your settings. But yes, if your controller goes kaput it can make the ECU pull or add fuel thinking your AFR is out of target. I believe it is the AEM UEGO that stays at 14.7 when there is a fault?

The fix is to make sure you have a solid ground. With MS2 there isn’t any error checking you can do on the controller to stop the EGO correction, so that’s unfortunate.

Have you verified the gauge and tuner studio (or your logs) show the same AFR? Those are notorious for having ground offsets, so worth verifying. And consider an X series if another controller is in your future.

Siks6

Old AEM was the UEGO X series 30-0300. The one I replaced is 030-0400. I will forward the log and tune files soon as I am at work now. I have placed it on a ground that shares with the PCM as well. The ECU was indeed adding more fuel to make sure it doesn't make knock when this happened. Gauge and TS show extremely slightly off, TS showing 14.7 while gauge shows 14.6.

Siks6

Here is the tune and latest datalog.

curly

iTrader: (25)

The ignition staying around -2.5-0 is because it's pulling up to 20 degrees of timing if it's off idle target. Your timing map around idle is all 7.7 degrees, which you should probably double. So if you're off idle target by 200 RPM, you'll be idling at -12.3 degrees.

In your warmup log, your RPM is matching target because of the idle timing correction, however you cut the log off at only 128 degrees, and even then you were already only around 4-6 degrees. I would increase idle timing to 14ish, and increase target to 950-1000.

As for the AFR, your tune isn't doing anything with it until 130 degrees CLT, and at that point it's able to adjust fueling by +/-25% everywhere, which is a lot. If your wideband is stuck at a value, which is usually full rich, full lean, or 14.7, it'll correct to match AFR targets without caring that the wideband isn't responding.

In the log you posted, I don't see anything wrong beyond a fairly noisy AFR signal, but at times it's as lean as 16:1, so I wouldn't expect it to idle very happily.

redursidae

Then you already had the X series, so that's good. To answer your question about losing ground or a controller while driving: Yes, it happened to me on an MS3 due to a broken wire and I was running an Innovate controller at the time. The MS3 CEL settings disabled EGO correction, so no weird issues as a result. I've also tested the functionality in Link ECU, which also disables the EGO correction when there is a fault. So the fix is to have a way to detect the fault and have the ECU not react to it. The AEM X series outputs > 4.5V when there is an error, and < 0.5V when heating (or unplugged?), but MS2 doesn't have a way to use those for a failsafe.

Curly beat me to the punch, but this is what I had typed:

If the AFR in your log is accurate, then your car is running lean at cold idle, and there is a lot of noise in the TPS signal. The noise could be caused by improper TPS calibration, or a noisy ground like coils or wideband controller. ITB tuning is highly dependent on TPS being accurate. The 030-0400 is new to me, but assuming the controller wiring is similar, there should be a sensor ground separate from the controller's ground. Which one are you sharing with the ECU?

If you can share a datalog of you driving the car at various conditions (warmup, idle, cruise, WOT), then we can check if the TPS is really an issue or not, and how the rest of the tune is behaving.

curly

iTrader: (25)

Try the attached tune. I added a bit of fuel, let EGO kick on earlier, made the ignition and idle target changes I mentioned, load it and see if it's "happier".

Siks6

I was blipping the TPS a bit just to get it to run without dying on me. I will get to that once I get a chance though.

Siks6

Thanks for the lengthy and well put response. I will give this a go when I get home.

curly

iTrader: (25)

We see the blips, it's when you're off throttle, it's a little concerning that it jumps around a lot in the 0-0.6% range.

Siks6

Oh that, yeah I will also investigate on that. I will recalibrate it and ensure all connections are good. I will do that either this weekend or after work today. I know when I did the ITBs, I had to do a full pin set up on the wiring, to ensure that the connections will be good.

Siks6

Update: Haven't had a chance to load in and check with a recent datalog, however, I have checked the TPS wiring. All wiring and connection is good. Will recalibrate before I upload the tune Curly has altered. I also should check my actual throttle pedal since I think it might've bent from totally not an anger issue from really really REALLY bad Colorado drivers awhile back.

Siks6

Alright Curly. I got a few logs this morning, all of these were mainly adjusting my TPS calibration. Finally got it to stop freaking out as you said. This was a combination of pedal assembly bending and making sure it's true open and close on the throttle bodies. The car definitely started up a lot cleaner. Idle was staying around 1.1 to 1.2k RPM. timing showed 7 to 8 degrees. This is the kind of throttle response I was hoping for. Super instantaneous and demanding to be pushed more. To simply put it: It reminded me of WKUK's Happier with your mouth open.

Siks6

Bump

redursidae

The last few logs look good to me as far as TPS noise is concerned, but your TPS stayed around 0.8 after a blip in the second to last log. Were you feathering the throttle? If not maybe they're sticking a bit? Check that the cable has a little bit of slack when everything is warm.

Did you go full throttle in any of those? I also don't see your TPS go to 100%. If you did, you need to recalibrate the TPS on turner studio to show 0 to 100% movement.

Your fueling is a bit lean up top, and rich at cruise. This could be off because of the TPS being mis-calibrated or recently messed with, so get that fixed before messing with the tune further.

Siks6

Yeah I don't recall going WOT, on any of the logs. I do have an issue with the assembly as it did get bent a little from people pissing me off on the road. (Colorado has plenty of horrible drivers that will even make the most patient driver rage). I will have to get megalogviewer set back up as I am now on a new laptop.

sixshooter

iTrader: (12)

Yes, leave a touch of slack in the cable for movement and thermal expansion/contraction. Mine was too tight once.

Siks6

Update: Figured out what was going on with Curly's adjustments and my set up. I had to basically readjust my idle screw.... yes, idle screw, once I did that, now I see my ignition timing closer to it's desired degree. throttle position seems more tame now.. Let me share in one moment

redursidae

Good to hear! If the car idles rough on a cold start you’ll need to open the idle screw a smidge and reduce the target timing when warm again. Otherwise you’re set in this regard!