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Discussion Starter · #1 · (Edited)
'09 XC70 T6 Engine stops immediately after startup

I have a problem with my 2009 XC70 T6 that has me and my Volvo mechanic stumped. The first time of the day that I start the car it works just fine. If I shut it of after it has warmed up and then try to start it again within 0-15 minutes (especially on hot days) it will start and rev to about 1500 rpms and then stall. Sometimes it will just stall completely sometimes it will catch at about 200 rpms and rev to 800 rpms multiple times and then stall. The gas pedal seems to have no effect during this period. If I try starting it with my foot on the gas it will not rev higher than it normally does when it first starts. If I try giving it gas when it catches at 200 rpms it seems to have no effect. This problem seems to be worse in the summer, and if I wait for longer than about 15 minutes to try to restart it, it starts without a problem. Has anybody else encountered this and been able to solve it, or does anybody have any good ideas on where to start?

Thanks!
 

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Was there a Check Engine Light? What things did the Volvo mechanic test?

I would hook the car up to VIDA or an OBD-II scanner that can graph engine parameters. I would look at the graph of the Throttle Position Sensor to see if
it is holding steady or closing up when the stall occurs. Same for Fuel Pressure. Same for MAF airflow. Fuel Pressure should be holding steady. TPS and MAF should start gradually decreasing about 30 sec. in, as the catalytic converter warms up.

These are some sensor inputs I would also check for erratic change coinciding with the stall:
- ambient air temp. sensor
- coolant temp. sensor
- barometric pressure sensor
- O2 upstream sensor
- O2 downstream sensor

My hunch is that the fuel-air mix is going lean or rich causing a stall.
 

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Discussion Starter · #3 ·
The check engine light does not come on until after it stalls and there has been no code logged in the ECU. I don't know what my guy checked but using a scanner that can graph the engine parameters seems like a good place to start. The engine runs great after it has started, which I would think would not be the case if one of the sensors was bad.
 

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The check engine light does not come on until after it stalls and there has been no code logged in the ECU. I don't know what my guy checked but using a scanner that can graph the engine parameters seems like a good place to start. The engine runs great after it has started, which I would think would not be the case if one of the sensors was bad.
One of the "invisible" things done soon after engine startup is the EVAP Test. If one or more EVAP solenoids are failing, there could be a rush of unmetered air when the EVAP test is run. I've seen somewhere that the EVAP Test is only run with the fuel tank between 85% and 15% full. So, there's a simple way to rule out the EVAP system....does it stall on a full tank of gas?
 

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Discussion Starter · #5 ·
It stalls on a full tank of gas, in fact I had to wait around at the gas station the other day for 15-20 minutes after I had filled it, until it would start. It also stalls/stops when I try to start it on a mostly empty tank.
 

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The engine temperature is a suspicious factor....when engine is hot, stalls out early in startup sequence. Wait 20 min. until it cools back down, OK to startup.

There isn't anything published I can find about the startup sequence. All I know is that when cold, the engine comes on at about 1600 rpms for about 25 secs, then gradually settles down to 650-700 rpm idle. This is done to warm up the catalytic converter (which has to be heated to scrub pollutant gasses).

Something in the engine control system is going unstable. We're back to hooking up to a diagnostic tool that can graph the engine input parameters in realtime.
The failure mode where the rpm bounces around between 200 and 800 should be very revealing when graphing engine parameters. If you can capture some pix of all the parameters graphs showing the glitch happening, that'll move the ball fwd.
 
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