Two problems related to engine knocking noise have been reported for the 2009 Subaru Impreza. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2009 Subaru Impreza based on all problems reported for the 2009 Impreza.
Engine knock sound while traveling on highway, pulled off next exit and car shut down. No check engine lights or oil lights indicating an issue. Upon restart knocking sound was louder and had a metal sound to it. I immediately shut the car off and called roadside assistance and had the car towed to local dealer. Upon first review dealer identified it as "internal connecting-rod bearing failure" which caused catastrophic engine damage. Subaru of America denied the repair due to the ecm being modified, stating "our engineers reviewed your file and deemed it to be caused by the ecm modification". I have found numerous cases of the exact issue on the internet, as well as a my dealership telling me there is a TSB for this failure. Soa is providing a "one time good faith repair" but I am responsible to replace the ecm. In my opinion this issue which soa is aware of and acknowledges with a TSB should be a recall - the engine failure at highway speed has potential to cause bodily harm - loss of power, engine seize resulting in an accident. I was lucky to not be involved in any sort of accident. Further I am totally unsure of how soa can claim the failure was due to ecm modification without ever physically seeing or having the motor pulled from the vehicle. The ecm modification is an excuse to not fully cover the repair.
2009 Impreza wrx there was no indication that a failure was going to occur before it happened. I had driven the car normally for almost 4 months. The engine began to make a loud knocking noise around 2000 rpm, sounding like metal hitting metal as I pulled up to a stop sign. Fortunately I had just entered my neighborhood so I was able to get home and have my car towed. Subaru road side assistance towed the car and I was given a rental for 20 days. Subaru dealer said it was a spun rod bearing and engine needed to be replaced. Even though I requested a long block replacement I only got a short block, so the turbo is the same. Since this occurred I have had numerous other problems, clutch throwout bearing replacement, starter, air conditioning problems. This car is a lemon but its impossible to convince Subaru of that fact. Engine blown at 3300 miles. Clutch problem at 7000 miles. Starter failure at 9600 miles (2/2011). Reported to soa.