Hi everyone,

I recently purchased from salvage auction a 2014 IS 350 AWD F-Sport with 210,000 miles. The car has a host of minor issues, but the one big one is that the car idles rough when in gear. When in park it idles around 800 RPM, but in gear the idle RPM drops to below 500 and the whole car starts to vibrate. The engine has stalled on me twice at this point.

I haven't done a ton of work on the car, but the oil and coolant is fine, and the car drives decently. If I rev the engine in park it sounds fine. I took it around the block and it drove fine until I tried to reverse to park when the engine stalled. I was able to restart it by putting it into park.

What should I start checking? I spoke to a few other people and we suspected: vacuum leak, sensor issue, bad ATF fluid (can I even replace this?), fuel system issue, or dirty throttle body. I didn't see any obvious vacuum leaks and the throttle body is blackened but is not dirty.

I have attached a video of the car running, but my phone doesn't pick up the audio well. The rattling towards the end of the video is NOT the engine sound, it's from the glovebox shaking due to the idling issue.

Thanks.

Have you checked for codes ?
Clean throttle body and maf, make sure air box seals properly, checked air filter element ?
Test o2 sensors ?

All I ended up doing was cleaning out the intake/maf/throttle body and disconnecting the battery for a while and that ended up resolving the issue.

Hopefully it stays running good 👍