In the last year or so at Bimmer Motors we have started to see timing chain stretch issues with the N20 engine. Customers will come to the shop with misfires on all cylinders and the engine on their BMW will randomly shut off when idling at a red light. We will start the process of diagnosing. If the computer doesn’t immediately throw a code for the engine being out of time we have to delve into diagnosing the issue. We will check the systems for spark, fuel, and air. As we eliminate the possibilities that could be causing the misfires and shutoffs we come to the conclusion that the timing chain has stretched.
We have found that out of the many possible reasons the chain prematurely stretches is the infrequent oil changes. BMW started recommending 10,000 mile synthetic oil change intervals which we have seen cause issues as these engines age. When a 10,000 mile oil change is recommended by BMW people tend to go even further over that mileage before changing the oil. The spent oil loses its ability to lubricate the chain and tensioners causing the chain to stretch and the engine to go out time, which means the engine is no longer synchronized.
Replacing a stretched timing chain on a BMW N20 engine is a laborious process, which requires special tools and knowledge to do the job right. If the job is done incorrectly and timing chain isn’t installed properly with the engine synchronized properly the misfires will continue at best or will cause your engine to hit metal on metal which will require you needing a new engine. That is why it is always a safe best to count on shops that specialize on BMW like Bimmer Motors to do these complicated jobs with a warranty.