Why does my car randomly stall?
I have a 2003 Volvo XC90 2.9 T6 (automatic) and it's been fine for the past couple of years (since we bought it second hand).
Recently though, it's been randomly stalling or not starting. Some typical cases are:
- Driving a couple of miles trouble free to pick the kids up from school, return to the car and it won't start.
- Slowing down to a stop, selecting reverse, starting to release the brake and stalling.
- Slow speed at a junction or roundabout, and stalling.
But, all of these are seemingly random. No regular interval (could be a couple of days, or many months), no adverse conditions, no other symptoms.
More recently, it's been idling a bit rough. Normally it's around 650 rpm, but it's hunting between 500 and 900 ish. A couple of days ago it stalled at a junction and wouldn't restart so it had to be recovered. The recovery guy plugged it in and had a 130a fault (leak near MAF sensor) so put it down to a vacuum leak.
Over the past couple of days I've carried out the following:
- Replaced as many vacuum lines as I could with silicon lines
- Tested and cleaned the MAF sensor (had a good 11.98v static and had a good correlation between acceleration and voltage from 0.xx to 2.xx)
- Checked the air filter
- Cleaned as many electrical connectors as possible
- Replaced the intercooler inlet pipe (it was spongy and blistered)
- I even removed and bathed (seriously!) the plastic air piping across the engine (from the filter box to the turbos, and from the turbos to the intercooler)
Started her up and it's now idling at around 500 rpm, which for the most part is smooth, but it can dip like it's going to stall (but doesn't). I don't think it did before, but now it feels like a slight hesitation when revving, which is much more obvious when revving hard and sudden. I put this down to the fact that the idle speed is lower than it was, but it stalled again and wouldn't start for a while.
I'm thinking the next thing would be to try to access and clean the throttle body but it's hidden away under the intake manifold and doesn't look so simple. But, to me this doesn’t explain why it wouldn't start.
Any advice would be very much appreciated as we have 5 kids and our beloved XC90 is like a 6th child