Can't seem to figure out this hunting AFR at idle issue. I have turned off closed loop, disconnected my ISC, set timing to 10 degrees in all idle areas to keep things consistent but the wideband still hunts from 14 AFR - Full lean at idle. Timinig is also inconsistent. Any suggestions? Attached is a graph, my ROM and a log.


Log Graph

 

Bump. Ideas anyone?

 

I don't have my laptop with me, so I cannot open the ROM. From what I see, this was a similar problem I was having when I went from MAF to SD, and much larger injectors; not sure about your setup. Once my injector scaling and latency was close; think we were able to get car to idle at 15.5 @1200 rpm. Then we were able to set idle to right around 1000 with bypass (?) idle set screw.

 

Hey Roro, thanks for the response. Your situation sounds a lot like what I am dealing with now. SD + FIC 1050cc injectors. What was your process to get yourself to idle steady at 15 AFR? I've been playing with latency and the VE tables but cant get AFR to stabilize.

 

Your TPS values are all over the place. If you aren't touching the throttle, you've got something going on there.

ISC steps are fluctuating too, but the TPS reading will cause that.

 

I think his log is idle and light throttle? I was thinking the same thing, but tabbing over showed there was mph on the log as well. I look at tps% (easier for me to wrap my head around whats going on). I was having issues when my tps was under 13% at idle. I had to look at old logs to see what my idle TPS% was because I removed my TPS to replace throttle shaft seals to fix boost leak. I thought I indexed the sensor properly...i didn't apparently. My old logs showed my idle to be at 14.5%. Once I adjusted to 14.5%, and got my injector scaling right, idle became steady (I was real lean, and hunted real bad....even after warmup). Make sure you hit operating coolant temps before reading vales and adjusting.

I think your scaling is still too high. My FIC's are scaled to 731; they are 950s.

Looking towards bottom of log, looks like you did a pull. AFR's look normal, I am assuming you are using a larger frame turbo, peak boost around 5k. This is same scenario I was fighting. I bet if it was hunting idle and you turned AC, it would stall.

 

Roro is correct, I posted a full log that included idle, light throttle, and a WOT pull. Sorry for any confusion that might have caused. I attached another log from the other day with just an idle log. (please note that my ISC is disconnected and closed loop is disabled)

Roro, turning on the AC does cause the car to stall, especially when it is hotter out. Do you mind elaborating more on what you mean by "indexing the sensor properly"? I checked my tps voltage and set it up in evoscan awhile ago. I think they are correct but another set of eyes is always appreciated.

I used a larger scaling number because my flow rates results were pretty good, I had them cleaned and bench tested prior to install. Attached an flow sheet, I have a newer one that showed them flowing better but can't find it at the moment. In any case, I'll try lowering the scaling after work today to see if it helps things stabilize.

 

Yes. The TPS is held on the throttle body by 2 screws. before I removed I marked the sides of the cover and the body of Throttle body. Once the screws are removed the TPS will clock/slide. It is held in place with a sprung tab (?), best way I can describe--at work and my brain is not working. After putting back together, if the lines didn't match up, the tps "starting" position will be off, and it will read different. (ie if it was reading 14% before removal, and it was slightly off, 11%, on re-install, The ECU will have a hard time finding what it needs for idle because it threw off the table (hope that makes sense).

I had to contort my hand and "modify" my stubby phillips screwdriver to loosen TPS enough, and recalibrate to 14.5% (taken from my old log at no throttle/idle).

When I get home, I will do a pull up evoscan and read my TPS voltage and see what the values are. Sorry I just use Throttle position for my logs.

I started scaling mine using references for FIC 950s on the Fuel Injector Scaling thread on this awesome forum. My injectors were brand new with the nice data sheet included. I think it called for me to scale 8xx. When I did, it was extremely lean; so kept going lower until car started to hold idle without me modulating gas pedal. That is how my scale is 731; nowhere near where I thought it should be; Keep in mind, my setup is on a seasoned stock lower block with 125k on it when I did this. It was previously on a methanol tune on 680 injectors on TME Turbo for the last 11 years.

I will pull your log when I get home and take a look. End of work day here. YAY

 

Had some time to do a few things this weekend. Started with a compression and leak down test. Numbers were good and consistent across the board. Also did a boost leak test and did not find any leaks. Last, I tightened the BISS screw to lower the idle a bit and lowered my injector scaling to 975. The AFR was slightly better and doesn't go full lean but it still hunts around. Next tried lowering RPM VE to get it to stabilize but it didn't help.

Attached and below are both an idle and cruse log with these settings, along with my updated ROM:

 

Is your coolant temp in Celsius and speed in KM?

Quick scan of your logs, your TPS is 0%? I do apologize, with holidays and kids schedule I have not been able to break into my logs or do current pulls to pull voltage references for TPS. Dont' worry about cruise right now; sort out idle; cruising will change after you get idle locked in.

But from what I see, your TPS needs to be recalibrated. Someone else could possibly verify what I am seeing, but at Idle you should be between 13 to 15% Leave the BISS alone (in fact set close to stock, I think it is 3-3.5 turns out from bottomed out; will have to look in Service manual again) until you have the hunting sorted out. I would start with the TPS calibration; Don't be afraid to scale injectors lower to richen up idle. Once you richen up enough, it should stop "hunting" and start to stabilize out. Make sure you are at operating temps when deciphering numbers.

Mine was the same way, and once my scaling was close, it solved the lean idle issues, and I was able to tweek afr's and RPM easily.

 

Thanks for noticing that my units got changed.. I'm logging with a touch screen laptop and I think the settings got toggled from Imperial units to metrics while I was driving the car. I'll post up a new log again when I get home.

As far as TPS, I believe I re-calibrated the eval in Evosvan at some point to get the percentage to show 0% at idle using this procedure: https://www.dsmtuners.com/threads/ho...ad-tps.428342/. For the physical calibration I followed the procedure for voltage sown below and set mine to 0.764 Volts, which may be slightly high. Do you mind checking your TPS volts at Idle and letting me know what you're at?:

 

Just wanted to update this incase someone else stumbles across the same problem. If anyone has AFR issues at idle like I did in the following video..


Here is how to fix it:
I performed the following steps in order and now my idle is steady at 14.7 AFR.

1. Adjust the throttle plate with the car ON and make that the throttle is fully closed but adjusted enough so that the plate does not get stuck closed. Doing this with the car on will allow you to detect the sound of your idle changing if the plate is adjusted too far. (My adjustment screw was initially too far in causing a small amount of air into the engine. Loctite also helps the screw from backing out.)
2. Properly set the TPS sensor to the correct voltage using a multimeter or logging device.
3. Recheck biss screw if you played with it after you get a steady AFR.