Stall in reverse downhill when come to stop
#1
Stall in reverse downhill when come to stop
Does anyone have any ideas about the stalling issue I'm having with my 2010 XF 5.0 V8? Here are the details:
- First start of day (cold start) but not necessarily cold outside. Temps have been as high as 60s or in the 20s.
- Backing down driveway on slight downhill, maybe 15 degrees from horizontal
- Hit the brakes and come to full stop (usually because a car is passing by on my street)
- RPM drops to 0.
- Car stalls
- Check engine light comes on
- I can "save" it if I take my foot off the brakes or switch to P.
- Restarts no problem in same spot on driveway
- After restart it will run in reverse at a stop no problem
- No codes
- Dealer had it for 3 weeks and could duplicate issue but had no idea
- Dealer opened case with JLR but still no idea
- Dealer suggested 5 hours of time to take apart car and check fuel lines
- Coolant temp sensor replaced by dealer just on a hunch but no help
- Petrol flange checked out okay (I had seen a video about a stall caused by a short on some electric connector on the flange)
#2
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#5
Live data from stall - help needed
Had stall this morning while recording live data on ALR 539B code reader. Data readout is attached. Stall was at frame 18 (out of 23). I've looked through the data but I have no idea how to interpret it. The most dramatic change I see just before the stall is in CATEMP11. It drops from over 900 (in frame 17) to 400 (in frame 18). I'm not sure if this means anything or if this data change is a clue to the cause or is a symptom. Also see load % go from 40s to almost 80, MAP goes up, and TP_R goes down right before stall but no idea what any of this means either. Can you please review the data and let me know if anything jumps out at you? I really appreciate any help or insight.
#6
It's a puzzle, not least because we can't see which original thing causes which others.
I'll try "thinking aloud"...
MAF drops to zero, which will mean no fuel is injected and a stall is inevitable then.
But why does MAF do that? I don't think the data shows that (but I could be wrong).
I suspect an air leak might do it, or the throttle closing, or an intermittent MAF signal.
Suppose it's the throttle, it could be any of a few causes, e.g. because the car (well, the PCM) thinks there's no/less demand (e.g. the accelerator pedal input says so, presumably in error), or the throttle plate itself could jitter a bit.
In case it's a sudden air leak... something flexing? A crack opening?
I'll try "thinking aloud"...
MAF drops to zero, which will mean no fuel is injected and a stall is inevitable then.
But why does MAF do that? I don't think the data shows that (but I could be wrong).
I suspect an air leak might do it, or the throttle closing, or an intermittent MAF signal.
Suppose it's the throttle, it could be any of a few causes, e.g. because the car (well, the PCM) thinks there's no/less demand (e.g. the accelerator pedal input says so, presumably in error), or the throttle plate itself could jitter a bit.
In case it's a sudden air leak... something flexing? A crack opening?
#7
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#8
#10
2011 XFR - I just had this exact thing start happening to mine, which is how I stumbled on this thread looking for answers. Cold start, after rpms settle for roughly a minute or two, throw it in reverse and start backing down the driveway (its not steep but also not level, hardly an incline), about 15 feet into reversing the rpms stumble and if I don't "catch" it by going full brake it will stall. Fires right back up though an no issues when warm or on the rest of the drive. Hoses all look good, nothing obvious, no check engines lights. It's truly odd and definitely hope someone could shed some light on this if they also experienced it.
#11
#12
I'd suggest possibly the brake booster vacuum is leaking down overnight, the first application of the brake delivering a larger-than-normal amount of air into the intake system which increases manifold pressure (i.e. loses vacuum), cold engine sensitive to the resulting lean mixture. Just a theory, possibly worth investigating.
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