2013 Mazda 3 2.0 Skyactiv A/T. After driving for a sustained period and coming to a stop, it has a mild vibrating/pulsating idle that doesn't seem quite right. It feels sort of similar to when there is low electrical power and the engine is struggling to maintain power (current battery is basically new). It doesn't always idle this way, seems to only be after driving for a sustained period. The car seems to operate fine otherwise.
Rough idle could be a number of things such as dirty air filter, dirty mass airflow sensor, idle air control valve may be dirty if your car has one it would be somewhere near your throttle body, it could be your spark plugs are going bad, maybe a vacuum leak, ect so go to autozone or any parts store and get a free obd2 scan from them to tell for sure
Thanks. I went to Autozone and they weren't helpful in doing a scan. They claimed their scanner was a really basic one that would only show codes for a check engine light. I didn't know what to believe, so I ended up just ordering the basic Ancel scanner Scotty recommends; it's about time I get one anyway.
I did a scan and there are no problem codes. Here is the full set of readings I got during idling if you wouldn't mind having a look to see if there is anything you think might indicate a potential issue: https://imgur.com/a/F9NsFDi
Test the MAF sensor. There should be a linear line between the g/s reading and engine RPM.
I've been doing some more research and I suspect the issue might be due to having recently replaced the battery and the PCM needing to relearn the idle. This seems to make sense since I don't remember it idling rough prior to replacing the battery, but I just had no idea about relearning idle so I never suspected the issue was related to the battery replacement. I need to detach the battery again this weekend for some other work I need to do, so I will try the idle relearn procedure, which involves letting the car idle for 15 min, then turning on the A/C full blast for another 15 min.
Good luck & please keep us posted if that fixed it.
After disconnecting the battery again for some other work, I did the relearn idle procedure and I haven't noticed anymore abnormal idle after a few days of regular driving, so that seems to have been the issue and has now been resolved. Thanks.
Seems I spoke too soon. After some higher speed and extended freeway driving, vibrating/pulsating idle again - only in drive though, not in park or neutral. RPM is steady, no fluctuation. I've come across some posts describing similar symptoms and mechanics who replied said it could be a bad engine or tranny mount?
I assume there is no code. Check the fuel trims.
I don't have a scanner but will try to get a scan. For the fuel trims, do the readings need to be taken while it is doing the unusual idling? Thanks.
That’s better. Take your cat to Autozone and have them scan it for free.
I finally was able to do a scan. No problem codes and the fuel trims seem within normal range -- here is the full set of readings if you wouldn't mind having a look and letting me know if you see anything that might indicate a potential issue: https://imgur.com/a/F9NsFDi
I would look closely at the IAC valve and TPS.
Thanks. I've been doing some more research and I suspect the issue might be due to having recently replaced the battery and the PCM needing to relearn the idle. This seems to make sense since I don't remember it idling rough prior to replacing the battery, but I just had no idea about relearning idle so I never suspected the issue could be related to the battery replacement. I need to detach the battery again this weekend for some other work I need to do, so I will try the idle relearn procedure, which involves letting the car idle for 15 min, then turning on the A/C full blast for another 15 min.