Stall at start/idle/stop - 2004 XC70

[br0dy519]

Thanks for replies guys.

Of course this started happening right after I filled a tank. Happened twice more today. I'm noticing it happens when you start the vehicle warm, like after being stopped after a drive. Had a weird throttle flare happen too. I'll be cleaning the throttle body and doing an adaptation in VIDA as well.

Still no codes except for an EVAP leak so I'm not convinced it's a coil. But I do have a spare new coil I can swap around and see if it makes a difference. I bought a fuel pressure gauge and took the below video. Any ideas from the gurus? After start-up it stumbles like crazy seems like it's "hunting" then stablizies to 60psi at 0:50



EDIT: I forgot to mention as well and update this thread back in 2021. I did purchase a genuine used TB from a 100k vehicle and that sorted a lot of the original issues out. Thing is I've probably put another 100km on it!

[br0dy519]

Dropped to 10PSI after the engine sat off for about 20 minutes. Just read a very interesting post from one of ( IMO ) best resources on the site, @jimmy57

The pump runs for a set period (1.5 seconds) when you cycle ignition on. It is normal for it to only go from 0 to 20 and then 20 to 40 as you describe. The pressure should be held after you shut it off after running to 25 or more psi for at least 20 minutes or it will have hot restart problems. If it goes to 0 overnight that is ok but if it drains back to tank completely then cold cranking will go longer. If it drained completely it would not get to 20 psi on that first short pump run.
The 55 psi initial pressure when started is normal too. That is a vapor lock clearing process to run pressure up to a higher amount and then settle back to 42-44 psi after 40-50 seconds.

[jonesg]

it looks like the pump is fine, you might have a leaky injector though.
That would cause a hot restart problem.

what is the pump duty cycle showing.?

if you install a shutoff valve in the fuel feed line before the rail you can prime it up to 50 psi then close the valve, that prevents the fuel from bleeding back.
If the pressure drops the injectors are leaking.
if the pressure holds the checkvalve at the pump in the tank is clogged or worn.

[Vova585]

Lets follow the data. Imagining the injector is leaking. OK you will have a slow(or sometimes fast) pressure drop. Affected cylinder will likely throw a misfire code due to the amount of fuel in it. In case it will not throw a misfire code you will likely have hard time staring(until all the air is primed and pressure back to normal) and car will start, will have rough idle and normalize.
If I remember correctly initial post was telling that car was starting, stalling and then was not starting. So leaky injector is a possible source of pressure drop, but unlikely cause here. I wish we would see pressure when the car is not starting and be able to see duty cycle of the pump and reported rail pressure.
I would likely throw a new bosch pump($135) and new fuel pressure sensor($35) at it and of not successful, would take to the dealer or other reputable shop.

[br0dy519]

Thanks guys. Unfortunately there is no duty cycle feedback reading in VIDA as this car has no PEM or FPS, the pump is just constantly on.
It is rare and strange but true unfortunately of my particular chassis. Also the fuel line is a hardline so it wouldn't be easy to install a shut off and knowing my workmanship I would cause a leak trying to. I did a simple test where I would unplug the injectors 1 by 1 and they really caused the idle to go crazy, so I'm not sure if it's an injector issue.

I did find some stuff this weekend while looking at the car.
1) I found my purge valve to be leaking, so I swapped it with the S60's functional valve and hopefully that fixes that particular vacuum leak.
2) I found the 3/8" heater hose from the thermostat to the PCV system to be leaking water on the damn alternator! My aftermarket radio has a voltage display, and I've never seen an abnormal reading as that was one of my first thoughts for the stalling issue. Always 14V running.

Fixed both of the above on Saturday and no joy, as the car did stall when coming to a stop after a warm start. Although it seems to be idling better now without that vac leak. I'm picking up my fuel pump today and will report back after installation. I'm also going to inspect and clean my MAF sensor even though it is new as of a year or two ago (genuine Bosch). Will check the rear of the car (J-hose leak maybe bad enough to cause this?) while I'm working at the pump.