In the last year or so we have started to see more customers coming in with issues related to BMW N20 timing chain stretch symptoms. Customers will come to our shop with misfires on all cylinders or their N20 engine will randomly shut off when idling at a red light. When the customer tells us the symptoms we start diagnosing. If the computer doesn’t immediately throw a code for the engine being out of time we have to check other systems to confirm the issue. We will check other system for spark, fuel, and air. As we eliminate other causes for the misfires of engine shut offs we indeed confirm that the timing chain has stretched.
What Causes the N20 Timing Chain to Stretch?
We have found that out of the many possible reasons the chain prematurely stretches is due to infrequent oil changes. BMW started recommending 10,000 mile synthetic oil change intervals which is okay when the engines are fresh and under warranty, but cause issues as these engines age and go out of warranty. It may be partly due to owner error as well, as owners tend to go a bit longer than the recommended 10,000 mile oil change intervals or change do their oil changes with cheaper oils. The used up old oil loses its ability to lubricate the chain and tensioners properly which cause the chain to get worn and stretch. Then then causes the bottom half of the engine with the crank and pistons to lose synchronization with the upper part of the engine that has the valve train. This is what causes the random misfires or the engine to shut off if the engine goes badly out of time.
The solution to the N20 Timing Chain Stretch
The only solution is to tear the engine apart and replace the stretched timing chain on the BMW N20 engine which is a laborious process. It requires special tools and knowledge to do it right. If the timing chain replacement is done incorrectly and the timing chain isn’t installed properly with the engine in perfect synchronization the misfires will continue at best or will cause your pistons to hit your valves at worse. That will pretty much require a new engine. That is why it is your safest bet to bring your BMW to a shop that has experience with European cars and has performed this repair many times before. If you have any questions relating to this or other European car issues, feel free to contact us at S-line Autoworks.