Car Starts and Dies after replacing booster vacuum switch

**jakehuman** · 12-27-2013, 05:53 PM

So basically I went to start my 2003 xc70 the other day and the car started revved up to about 1500-2000 rpm then died. I took a look under the hood and I noticed that the booster vacuum switch (looks like three prongs with an electrical outlet attached to the top) was cracked and hanging in the engine compartment. I promptly replaced the entire switch with a new one from my local volvo dealership.
Now, the car starts runs for a few seconds (much better than it was before) but slowly dies. It sounds like the car is not creating a proper vacuum, but I suppose it could be something else fuel related. I am most certainly no expert. I have perused the forums for a similar issue and have come across no such problem.
Was the issue with the vacuum switch related or was it just coincidence? \

Thanks for reading,

J

Also the best way to describe the sound is when you start up a gas goped but you haven't pumped enough fuel into the engine or let it idle for long enough before accelerating. (If it helps at all).

**Scopeman** · 12-27-2013, 06:04 PM

Are you sure the vacuum lines are hooked up correctly? I think it has a check valve.

**hoonk** · 12-28-2013, 10:56 AM

The vacuum switch for the brake vacuum pump usually (as i've seen) breaks the electrical switch portion off the top and then the pump does not run. Most people have no clue it is broken because it does not create a (substantial) vacuum leak or any other problems that they notice. (and does not seem to store a fuel trim code due to an air leak) When it is broken it can make the car hard to stop especially when first started due to lack of vacuum assist.

All that said I don't think your running/stalling problems have anything to do with the broken brake vacuum switch. (as long as it was installed correctly) Is your check engine light on? Is the car low on fuel and parked at an angle? Is there evidence of rodents under the hood of your car that may have damaged wiring? When was the last time the car ran correctly?