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My purpose in creating it is to help gauge the number of G37 A/T owners that experience an inconsistent idle when in Drive and possibly leverage the resources, knowledge and tools available within this community to uncover the root cause of the issue.
If you're unsure and drive a 7AT, I would invite you to read below then monitor your idle speeds for a week before voting.
A little background on what I’m referencing and what many users here and on YouTube are also experiencing:
The specifications for the idle, according to the FSM, are that the engine should idle at 650 RPM, +/- 50 RPM, when the engine is warm, climate controls are off, radio and display are off and the wheels straight ahead (I’ll post a pic below). Impacted vehicles have a noticeably lower RPM in Drive than in Reverse, Neutral or Park.
For my vehicle, once warmed up the idle speed in Park, Neutral and Reverse is all close to spec when eyeballing the tachometer; however when in Drive the idle drops considerably to around 500 RPM (again eyeballing the tach). However, periodically and for reasons that haven’t been proven, the idle in Drive is at the same RPM as when in Park, Neutral and Reverse. It’s this inconsistency in behavior that leads me to believe this isn’t how the vehicle was designed. I now have scan tools and am currently pulling logs from the PIDS but this scenario is generally what everyone who has this issue experiences. For myself and others it seems that once the power train is thoroughly warm the vehicle idles correctly in Drive. This could be after a spirited drive or, at least for me, if I drive it for 20 minutes then park in the garage for +/-60 minutes it idles correctly.
Only one user, Jsbach1685, has come close to resolving the issue as he found a dealer last week who would raise his RPMs to 700. The results so far have been promising for him in his thread. Otherwise, we’ve cleaned throttle bodies and performed the relearn procedures to no avail. As I mentioned a moment ago I am pulling logs to see what’s different when the car is idling at 500 in Drive and when it’s idling at 650 in Drive.
I have a collection of videos on YouTube and some pictures from tonight that I’ll post below.
-Eric
Cycling through Park - Reverse - Neutral - Drive - you can see the RPMs drop when going to drive:
Why create a poll? Erratic idle and improper rpm while stopped in drive is almost always dirty MAF/throttle bodies.
Great question!
Generally, I agree. However, in this case TBs have been cleaned, MAFs have been cleaned/replaced, along with plugs, PCVs, fuel dampeners and other various fixes to no avail. Usually the user experience would be consistent, i.e. rough idle, slow off line, etc. but with this there are days when the vehicle idles the same in Drive as Reverse (meaning the ECM might be compensating when in gear) and other days the idle in Drive is low as in my pictures above. This lower idle in Drive does lead to a slightly rougher idle which is often how it's first discovered - and I ask those that don't know to monitor their idle speed for a week to determine if their idle is erratic.
I see you have a 7AT - do you experience a different idle in Drive than Reverse? Approximately how many miles (theory with higher miles)? And are you stock or tuned?
As a follow up - beyond gauging scope of the issue, my hope is to engage members such as yourself to bring technical knowledge to the conversation and group think ideas.
As my vehicle (and others) seems to idle differently once the power train (engine, transmission and transfer case) are thoroughly warmed up, my hypothesis is the ECM may not always know that it's in Drive. According the multi-port section, the ECM modifies the fuel when the vehicle is in Drive and the TCM appears to pass that trigger to the ECM. As the TCM is housed within the transmission, is it possible it isn't communicating the vehicle is in Drive until it warms up, possibly indicating a cold solder within the TCM? I attempted to gather PIDs for the transmission temperature, but according to @MotorvateDIY the only way to get this information is with Consult as the vehicle needs to be put into a diagnostic mode first which isn't possible with OBDFusion. I am capturing throttle information which seem to indicate the throttle (absolute throttle position) is different when the vehicle is idling at higher RPMs in Drive.
I see you have a 7AT - do you experience a different idle in Drive than Reverse? Approximately how many miles (theory with higher miles)? And are you stock or tuned?
I spend so little time in reverse I don't know. And when I am in reverse, I'm looking behind me or at the back up camera. I'll make a point to check next time I back the car into the garage. Car has 54k miles or so. Stock tune. Idles the same 650 rpm whether in park or drive; throttle bodies and MAFs have never been cleaned.
2 logs below:
CSVLog_20191104_075606: Started vehicle overnight cold (garaged, +/- 55 degrees) around 7:56 am. Drove son to school then daughter to bus stop, total trip around 25 minutes and the engine was thoroughly warmed. Towards the end of this trip I sat in Park for an extended period of time waiting for the bus, then drove several blocks home and put it back in the garage - idling below 600 in Drive.
CSVLog_20191104_091709: Back in the car after about 50 minutes of sitting in garage. Coolant temp had dropped but after a few minutes vehicle was again at temp and idled correctly in Drive for the rest of the trip to work. The climate controls were off for the trip to minimize engine load and I idled in Drive for several minutes at the end. There's also a video below from the end of the trip that corresponds with the logs.
Looking for any insight on what the logs indicate (if anything) and what else I should log. It seems that I need to have more than a warm engine for the vehicle to idle correctly.
Little pre-winter maintenance @87k miles - haven't noticed a change in the idle but I'll keep logging. We're in a cold snap here (IA) so great time to see if it idles correctly after just the engine is warm.
I did notice that the temperature gauge reads "normal" when the engine is about 150 degrees and doesn't change position as it warms to 200.
Oil change and filter - Mobil 1 with Mobil 1 extended filter
Coolant drain and fill - Valvoline Zerex blue, new o-rings
Cleaned MAFs and throttle bodies
Replaced air filters with Bosch
Idle relearn with NDSIII
Ran out of time for Seafoam - probably Sunday along with cabin filter
- Eric
TBs weren't bad - only been about 20k since cleaned
10-30-2019 | 09:43 PM
