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Discussion Starter #1
Today the car (2004 S500) was jerking when driving and stalled when idling several times. It stalled also when I increased engine RPMs from idle state.
DAS shows that no error codes are registered. Drived a bit more now seems to be ok again.
I have had previously quite a few occurrences when it felt that the car is jerking, but today jerking was in a row and several stalls while idling.

Any ideas where to start debugging? Shouldn't there be an error code in MFE ECU if that was due to misfire or similar?
 

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Hook up fuel pressure gauge. DAS will tell you that light in spectacle compartment is out but will not store any codes when fuel pump quits. 馃槙
 

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My friends 2008 S550 had same symptoms, and then it quit on the highway. NO codes.
Hooked up fuel pressure gauge to schrader valve (passenger side on fuel rail) No fuel pressure.
Tested the fuel pump connector under the rear seat, passenger side, and it had 13 volts when he cranked it.
Replaced fuel pump and filter. No more problems. His car had 104.000 miles, and fuel pump was the original.

Sorry for the intrusion, but post just caught my eye when I was looking for something else .
 

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I had a similar issue with my '04 S430. I did two things at once and the issue went away - so I'm not sure which one fixed it. Jerking only happened at slow speeds or stops - car seemed normal at higher speeds.

I replaced the EGR valve with a new one.
I replaced the gaskets on the valve covers (mine were leaking oil at the time).
 

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Discussion Starter #5
Here is video from non-smooth engine run:

Here is video with two stalls:
The coughing sound in the 3 second (after stall) comes from engine.
The pump needs replacement because it is releasing fuel back after engine is not running, but what do you think about these stalling moments? Are they fuel pressure related? (note: the moment when fuel pressure becomes fixed/stable is the moment when engine switches to LPG. Stalling happens also when not running on LPG)
 

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Indeed I noticed some fuel pressure related problems may not throw codes but should eventually, at least in your case you may eventually have system too lean codes, mixture formation related. What type of scanning device did you use? There may be codes, like the p1999 (p203-02), may be available only when reading manufacturer codes and the p1999 is there when there are fuel related problems.

Other things to try:

1. Unplug MAF and check behavior
2. Establish the catalytic converter is not clogged.


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