Intermittent long crank (Timing Chain issue?)
My car has 75000km and intermittent long crank for a few seconds. It will then start up and run smooth every time, but with CEL. The problem usually happened if the last trip was short (3~4km) or long (over 30km) but with the engine eco stopped a few times. Otherwise, there would be no problem at all. I also tried a few trips with the ac off and can always get instant crank and start at the next time.
A friend helped to pull out the fault code P034062 and, base on which, suggested to change the timing chain and the cam sprocket. I did some search and note that the stretched timing chain and worn cam sprocket issue is common for M271 engine, but want to make sure it is relevant to my case or the code before open up the engine. Would my problem be related to the state of charge of the battery instead? But the battery was just bought three months ago.
Besides the occasional long crank, CEL and the code, I can hear some deep (not loud, but noticeable) “dud dud dud” noise from the front panel inside the car at idle. Other then these, the car runs smooth (but I may be too dumb to notice subtle differences) and the fuel consumption is like new (sure for this). Would this be possible with a stretched timing chain?
Where should I start from? Any idea? Many thanks.


