I have a stalling and starting problem on my 2005 119P Vito (M112 engine) with 70,000 km. MB have run diagnostics and say nothing is wrong and if problem not repeatable in their presence then they can't fix it. At 100kmh cruise without warning the engine 'backs off' ie the speed decays to around 65kmh. It is as if you have suddenly taken your foot off the accelerator. After the few seconds of 'stall' the engine runs slightly rough then picks up to normal again. This can be pretty dangerous when there is a semi-trailer barrelling up behind you!

The stalling began on 20 Feb 08 when the engine slowed to a complete stall from 110 kmh as if I had taken my foot of the accelerator. No alerts were shown on the dashboard. I pulled over as the engine shutdown completely and waited 2 minutes by the side of the road and restarted the engine (1/8 tank of fuel). When I refuelled about ten minutes down the road the engine start required extended cranking with rough running before idle was established (3/4 tank). This was the first time I had ever experienced any engine start that wasn't almost instantaneous.

The stalling failure has occurred about thirty times since Feb 08 and can best be described as, ‘it as though you have lifted your foot off the accelerator’ and occurs without predictability but almost always from a road speed of 100 kmh (once from 80kmh) (suspect Crankshaft Position Sensor, Camshaft Position Sensor, Electronic Throttle [pedal position sensor, throttle motor, wiring or connectors], fuel pump, fuel pump relay, MAF)


Also when cold starting the vehicle it now often takes two goes to successfully complete the start cycle. ie it will crank and crank and usually fire but only at the end of the cycle just before it times out. On a good start it fires immediately and settles to smoothe idle. On slow start days the eventual firing is quite rough before idle settles. To guarantee a predictable start just crank briefly and turn off and then try a re-start which occurs immediately.

MB have had the vehicle for over a month across several occasions and claim never to have witnessed these problems. When I get the vehicle back the problems occur at almost the same frequency/symptom. I cannot understand how a vehicle of this generation can have such significant faults with nothing recorded on the diagnostics!

One area I suspected was the Crank Position Sensor which has been a problem with stalling on MB cars with the M112 engine. Apparently faulty CPS won't log a fault code until they are totally stuffed but will fail intermittantly for some time. I eventually convinced MB to replace the CPS regardless of codes but this has not fixed the problem.

Some have suggested it may be a fuel pump problem as these have been known to fail early. Is there some way to monitor fuel pressure and flow so I can see what is happening when the fault occurs? Why wouldn't the ECU diagnostics record a fault if these parameters were faulty?

The only other issue I have just noticed is a 'tinkling' sound when engine is revved while parked. This sound is coming from the most upstream catalytic converter on the right bank. It sounds like the ceramic core has come loose or a piece broken off which is rattling against the cat housing on the low side, downstream. No impact damage or exhaust leak is apparent.


regards,
Damian from Melbourne, Australia