Subaru stalls


I have a 2003 Subaru Legacy wagon, only 59000 miles, and it has been stalling when coming to a stop after driving for 20 - 30 minutes. The check engine light would come on. The dealer checked the code (P0519) and determined the idle air control needed to be replaced, which was done. However the problem is still occurring, same error code and stalls when slowing down to stop after driving steady for a half hour. I was out of town and went to another dealer who checked the code and it was the same issue. This was NOT an inexpensive part to replace, but the other dealer states that the new IAC has tested OK but now it’s possibly an issue with the ECM or wiring. Could the ECM be causing the car to stall like this? It looks like the mechanics are stumped and I’m paying for it! Any thoughts? Thanks.

Is the stalling associated with braking? I.e. does it always coincide with you hitting the brakes?

The code is triggered by unmeasured air getting into the engine. One thing that can cause this is a faulty IAC - but that’s been eliminated as a problem the expensive way. The other likely culprit is simply vacuum leaks or perhaps a dirty throttle body. A cleaning of the Mass Airflow Sensor wouldn’t hurt either. Someone needs to check the whole intake, throttle body, and vacuum lines for leaks.

I ask whether it is associated with braking because a failing brake booster is one way to end up with a sudden vacuum leak large enough to stall an engine.

ECM would be good news. It would be covered by your 8yr/80,000 emmissions warranty.

Maybe suggest it as a fix on Subaru’s dime.

I don’t think it’s braking, since it happens when I just downshift and let the car slow down. The throttle body and leaks could be a good route to take - thanks.

Here is what the code means: Idle Air Control Circuit System Performance

Like the shop was thinking, the wiring between the device and the ECU needs to be checked out for a problem. Not a hard thing to do.

I took it to a private shop locally and they have fixed it. Turned out to be a faulty neutral safety switch. I do not know why two dealers could not figure it out. Thanks for all your help.