98 S70 t5 Rough idle sputter dies often

netguyscott · Post by **netguyscott** » 28 Oct 2014, 18:22

I did use MAF spray on the old MAF, but didn't notice any changes after the cleaning, hence why I went with getting a new one. Hey last night I did discover something in my hunt to fix this. As I said before this car sat for a period of time with a cracked radiator and along with that it had an old (2004) dead battery. After removing the new battery and the battery tray below it, I found some kinda gizmo attached to the underside of the tray that had a little acid damage to its case but appears fine. However, there's a hard plastic hose that runs from it and follows under the air cleaner and its badly cracked, so would definitely be leaking. I looked up the pump-- it's labeled 1390903 and its called a vacuum booster, and is part of the Cruise control system. Could that be causing any of my rough idling problems??

Post by **FLXC90** » 28 Oct 2014, 18:26

It could-it is a vacuum line. tape over the holes in order to test it if need be, then replace if needed

netguyscott · Post by **netguyscott** » 28 Oct 2014, 18:31

That isn't the main vacuum pump is it? It's listed by the Volvo dealer as a part of the cruise control system, and referred to as a vacuum booster. Amazed they put a pump under the battery tray.

Post by **abscate** » 28 Oct 2014, 22:02

It's part of cruise control and could be your idle trouble. Leaking vacuum hoses will kill idle.