Okay. I've got a 2012 gt. The only motor mod is a "race" Airaid CAI. I don't have my tuning laptop with me, so the questions I'm about to ask will need to be answered with concepts/hypotheses until I can post my log and tune. But please respond barring these!
The issues I've had with the car since I've had it is hunting idle. When I bought it, it had the CAI, but it had the sleeve still in place, so the tube ID was closer to stock. Then, I removed the sleeve, adjusted the MAF curve to account for the increased airflow, and I did some OP spark tuning. As you will see with the majority of my tune - most of the changes I made were to affect WOT behavior by reducing WOT pedal position, WOT VCT events, and increasing the WOT spark (OP borderline and MBT tables). I also have done a little bit of trans tuning (automatic car), but that's irrelevant to my issues.
Back on track. When I cold start the car, it idles according to the setpoint and adders I've defined, initially (for maybe 10 seconds or so), then it starts to vary approximately 200-300 rpms at a slow rate (as opposed to a fast oscillation). Mind you, it will stay in idle feedback source (can't remember if this is an idle source or a torque source PID) the entire time this is happening, which seems weird to me. I would expect the source to jump around for something like this. Anyway, once it gets to operating temperature, the oscillation seems to go away.
Another issue I am having is when I blip the throttle in park. After a "blip event", I'll call it, the torque source goes to target N, which seems normal as it is trying to achieve the commanded idle setpoint. But when it does this, it aggressive pulls the RPM to around 500 and hunts pretty badly and takes anywhere from 5-10 seconds to finally stabilize and get back into idle feedback mode/my desired idle speed. Does anyone know what causes this? Car doesn't have an aftermarket throttle body to my knowledge. The reason I say this is because the TB model values were all stock when I bought it. Granted, it has always hunted idle, like I mentioned. It just worsened after I removed the CAI sleeve. So maybe this is something I should check. I have a 99% feeling it is stock though, since the car runs great under all other conditions (cruise, partial throttle, WOT, etc.). I messed with the idle spark tables a few years ago (before the "race" CAI) and I didn't like the way it reacted, so I changed them all back to stock. I recently lowered the spark torque reduction strategy in an attempt to lessen how aggressively is pulls the engine speed down during target N. Doing so resulted in intermittent results where it will gradually pull the engine speed down if a lightly stab it and wont hunt so badly (yay!), but if I flog it and let off, it remains relatively unchanged (still aggressively pulls the engine speed down and hunts badly afterwards).
A new problem that developed recently, and I have no idea why, is that my log is showing me that it is cutting the fuel injectors by going into fuel source "(OJ) fuel inj cut" when I'm in 1st gear and lugging it (<5% or so throttle). I've read in another few threads that this fuel source can happen if there is an issue with the ignition system, via bad plugs or coils. If I understand correctly, the ecu is smart enough to detect a misfire and then turn off injectors to prevent cylinder flooding. Pretty cool, except for when it's happening lol. I haven't received any misfire DTCs though, so I don't think it is this. Another thread mentioned that if one's MAF calibration is way off, then the car will go into OL. Is this true? Interestingly enough, when the car is doing the weird, aggressive idle hunting mentioned above, I see MAF periods in the 500ms or so and fueling correction (STFT) going to 20%. This has happened to me a few times. I keep adjust that point of the MAF curve by multiplying by half (I've done this two or three times already), and I keep seeing STFT go to 20% in that part of the curve, which is weird. But the STFTs during this mysterious injector cut are all within 3-5%, plus or minus.
I also tried adjust the DD table at 12 pedal counts and 1150 RPM, but it didn't seem to do much. Granted, I barely changed to value from stock. Could this be my problem?
When I get back home I will see if I do have an aftermarket TB, and I'll check my plugs. And as I mentioned, I will post my current tune and log so there is more to go on. But in the meantime, can anyone lend some credence to my thoughts and provide the "whys" for the issues I'm having.
Please help! I'm desperate at this point!
Reply With Quote
Originally Posted by White12GT
