Sorry – it has been a long time between posts. I see there has been significant activity on this thread since I last posted. Here is an update.
Earlier this summer, I had Japanese engineers come to my house and drive up the hill in my vehicle. The regional technical specialist has come as well on a couple of occasions. I cannot say enough good things about this technical specialist as he has been very professional and attentive. I didn’t interact with the Japanese engineers, so I do not mean that previous comment to imply they were any way, shape, or form unprofessional. I just haven’t interacted with them directly. In fact, the reality that they were willing to fly out and come to my house is a strong statement otherwise (they remained out in the car while the reg. tech. specialist came to my door to get the CX-9). I just intended the previous comment to be a sincere compliment to the regional technical specialist. Mazda has a got a very good one with him and is lucky to have him.
At any rate, Mazda acknowledged the engine knock. I provided them with a DVD of the underhood microphone recording and a DVD video simultaneously recorded using my Sony Handycam within the cabin. The Handycam rested on the dash and looked out the windshield while driving. The mic on the Sony Handycam did pick-up the engine knock; it just wasn't naturally as distinct as the recording from the underhood microphone. Regardless, the two recordings perfectly correlated to one another nonetheless. I also had a colleague perform sound analysis to prove the recordings were one in the same, and to further help Mazda, I had him overlay the underhood recording to the Handycam video recording to create a new movie file to show exactly what the terrain looked like when the engine knock occurred.
So in summary, I provided Mazda with (1) the original sound and video from the Sony Handycam recorded inside the cabin while driving, (2) the simultaneous USB underhood microphone recording plugged into my laptop sitting on the passenger seat, and (3) a digital combination of the Sony Handycam video overlaid with the underhood microphone recording for further diagnosis.
As for the video, it went well beyond the recording of just the engine knock events alone. It also showed the complete setup for the underhood microphone (including the start-up and stop of the recording from the underhood microphone), the vehicle mileage, date (further supporting by recording turning on my cell phone), the gas in the tank (including recording exactly where I got the gas, the gas being pumped into the vehicle, and the type of gas put in the vehicle), the engine shutdown after recording the engine knock demonstration, and complete post-test inspection of the setup to prove nothing was disturbed during recording.
Also, the Japanese sampled gas from my local station (I went out of my way to fill with gas that had no ethanol in it -- not just for the sake of the CX-9 -- but for all my vehicles. You could do it back in the late spring / early summer, but now it is very hard to find a station that does not have ethanol. As previously mentioned, part of my video recording provided to them documented exactly where and what type of gas I was putting in my vehicle prior to demonstrating the engine knock). I never heard back regarding the results of the gas sample, but I assume it was deemed "normal". While I didn't offer it and they didn't ask, I also had additional DVD recordings/ underhood microphone recordings documenting engine knock with full tanks of gas used from a couple of different gas stations and gas companies. However, since it was a non-issue, I concluded it was unnecessary to provide. I just had it as back-up in case I needed it. I hate to sound so cynical as my experience with Mazda Corporate has been very good thus far, it was just that my experience with my local dealer was so awful it drove me to this point / level of documentation. Trust me – this was NOT my first course of action or first choice. But after the brake booster runaround (didn’t apply to my vehicle), denial of the knock, an unwillingness to help, horrible communication (kept vehicle for two weeks and never bothered to call to say it was ready), and multiple experiences of all the above, my trust bank was on empty with the local dealership. Again, now working with Mazda Corporate directly, it has been a complete 180 and a very positive experience.
So long story short, I got a new engine. Mazda shipped the engine from Japan for my CX-9 in the early summer. The old engine was pulled and shipped to Japan for further analysis and the new engine installed. We’ve put about 6,000 miles on the new engine and thus far have not heard any engine knock. I have not gone so far as to put the USB microphone back under the hood, but I can say thus far I no longer hear the engine knock inside the cabin. Whether an official TSB is posted or not out of this is TBD. I suspect we are a guinea pig for a solution for vehicles that experience this problem, and I am happy to work with Mazda on a solution. The number of vehicles affected is between the general public and Mazda – I have no idea. I just know our vehicle was one of them. With any luck, the new engine will continue to not knock and be a permanent solution.
As for the underhood microphone recordings, it is very simple to do. USB microphones are inexpensive and easy to get (try Amazon and see for yourself). Just secure / tape the mic near your battery, run the cable out the back of your hood and in the passenger side door (just close the door over the cable), and plug into a laptop. It is really just that simple. However, sounds like folks have got some very good recordings just using their cell phones under the hood. Pretty much the same idea with no laptop required.
If anything changes in our experience or if there are new developments, I will let everyone know.
Any how, the premium gas seems to take care of the knock. However, I noticed the mild knock again when pulling into my driveway on regular unleaded.
