[mwd]

We just put new dual exhaust and a Cold Air intake on our 2004 V6 (manual trans). We then put an SCT Custom Tune in for 87 Octane/performance. Car runs great except when knocking out of 5th gear into nuetral/idle. Every once in awhile, it will stall under those conditions. Car idles fine in the driveway or whenever stopped in traffic. Have noticed that when coasting into a red light (in neutral), the rpm oscillates from 400 to 800. Sometimes it won't recover from the low side while it oscillates and that's when it stalls (only when rolling).
However, when sitting still at the redlight, no idle problems at all. What the heck is this??

Cleaned the IAC, wasn't really that dirty. MAF was clean. As a reminder, this is a manual trans. Any suggestions? Thanks.

[RFM 40th V6]

This is a long shot but have you checked your clutch adjustment? Are you sure that the clutch is fully disengaging?

Also sometimes just cleaning the iac isn't enough, if it's worn out you'll need a new one.

[mwd]

Yea, I was wondering about something in the drive train as well but, the clutch not fully disengaging would still be an issue while sitting still. I'm leaning towards that IAC replacement or maybe something with that new tune we just got. Sound reasonable?

[RFM 40th V6]

It is possible that the new tune would be leaning out the mixture too much.

I'd go after the IAC first though.

[mwd]

Went back to stock tune. Oscillation still there while rolling so the issue/cause is still there. No stalls yet though. Will give it a little time, then go after the IAC. Thanks.