Hi all,
So like some others around here, I've had occasional rough-idle issues while in gear (6-sp auto) at red lights and such. Some people have indicated it was a manufacturing defect in the transmissions, while others (like myself) have had off-and on experiences. Sometimes it's bad to where it causes the seats to vibrate in the car--sometimes silky smooth.
Since the car is under warranty I've taken a "not my problem" attitude toward the issue (it's not like I can't use the car), but slowly frustration has mounted. The dealer has run several cans of GM fuel system cleaner, and I've been using nothing but Chevron gas for several months, with no positive improvements.
Thus, it's time to whip out my really nice OBD2 scanner.
So I tooled around in the car for about 15 minutes and I noticed some odd behavior by the computer. Wondering if someone else out there with a 2012 1.8 auto could verify my data.
Upon warm starting, the reported idle RPM is exactly 680, with some acceptable up and down variance. Pop the car in drive, idle is still at 680--however noticeably shaky. Accelerator position clearly shows the ECM giving it more gas to keep the RPMs up. No big surprise--other than maybe 680 RPM. Seems a tad low?
So, now--with the live data still streaming, I kick on the A/C--RPMs jump to 780, exactly 100 higher. Again, no big surprise here. But the interesting thing is the car completely smooths out. Almost as if--it was supposed to idle at 780. Again, in gear or in neutral: 780.
Now the best part.
Turn the A/C back off. Idle stays at 780. WTF?!
I sat in the car for 5 minutes and idled. 780 RPM.
Figured, what the hell--drove to 7-11 and back, A/C off. 780 RPM.
Sat in the driveway, turned the engine off and restarted. 680 RPM. Rough idle is back.
What the heck GM?
So like some others around here, I've had occasional rough-idle issues while in gear (6-sp auto) at red lights and such. Some people have indicated it was a manufacturing defect in the transmissions, while others (like myself) have had off-and on experiences. Sometimes it's bad to where it causes the seats to vibrate in the car--sometimes silky smooth.
Since the car is under warranty I've taken a "not my problem" attitude toward the issue (it's not like I can't use the car), but slowly frustration has mounted. The dealer has run several cans of GM fuel system cleaner, and I've been using nothing but Chevron gas for several months, with no positive improvements.
Thus, it's time to whip out my really nice OBD2 scanner.
So I tooled around in the car for about 15 minutes and I noticed some odd behavior by the computer. Wondering if someone else out there with a 2012 1.8 auto could verify my data.
Upon warm starting, the reported idle RPM is exactly 680, with some acceptable up and down variance. Pop the car in drive, idle is still at 680--however noticeably shaky. Accelerator position clearly shows the ECM giving it more gas to keep the RPMs up. No big surprise--other than maybe 680 RPM. Seems a tad low?
So, now--with the live data still streaming, I kick on the A/C--RPMs jump to 780, exactly 100 higher. Again, no big surprise here. But the interesting thing is the car completely smooths out. Almost as if--it was supposed to idle at 780. Again, in gear or in neutral: 780.
Now the best part.
Turn the A/C back off. Idle stays at 780. WTF?!
I sat in the car for 5 minutes and idled. 780 RPM.
Figured, what the hell--drove to 7-11 and back, A/C off. 780 RPM.
Sat in the driveway, turned the engine off and restarted. 680 RPM. Rough idle is back.
What the heck GM?
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