So under less then desirable circumstances i recently inherited my son's 2007 MS3. He really liked this car and inwant to keep and maintain it for him. I'm no stranger to turning wrenches but don't claim to be an expert by any stretch, my biggest obstacle is the turbo. Fully understand how they work and such but it will be a learning experience. He bought the car 07/2022 and from what we found, and i have learned myself, previous owner has made multiple upgrades. Best i can tell/guess they are all bolt ons. So far i have just been ironing out the maintenance things it needed like tune up end links etc. The only thing i haven't yet confirmed is when it first starts engine idles and sounds fine. But once it warms up makes a rattling sound from rear passenger side of engine compartment. Using Torque app not seeing anything stand out on gauges except when accelerating voltage dips a little so think it maybe alternator going bad. Hope to confirm that in next few days. Otherwise look forward to learning more about this car and continuing what he started.
Glad you are here! Double check all three alternator bolts are installed, air cover for cooling not broken off. Accessory belt tensioner bearing for pulley not rumbling. Has valve cover been off yet so you can check cam chain tension and VVT? Always a good check on current state since it's a expensive repair if not done recently.
Alternator cover look fine, no signs of cracking from what i can see and all bolts look snug. After checking with load tester i think alternator regulator maybe going out. When i start car up and has 13.9-14 volts. If you rev up slowly bounces a little from 13.7-14.1 but if you let go of gas volts drop to 12.7-12.9. And that is with nothing on like lights, stereo etc. Any load and instantly drops to 12.3 volts and then slowly rises back even if your holding at 2000 - 3000 RPMs. Has yellow top battery that holds charge so don't believe that is issue. On several occasions while heavy acceleration and stereo playing fog lights flickered. Which leads me to think voltage is not consistent and alternator cannot keep up. Visually i can see oil leaks from valve cover and the vvt valve cover gasket. So that is on my list of things to do and figure that will be a great time to check chain tension. Otherwise for most part car is pretty solid and runs strong. Never feels like it stops pulling when boost spooled even in 6th gear. It's a fun little car and i see why my son liked it. I'm curious if anyone can say but on a factory MS3 does the exhaust have a low tone with almost a small pop at idel. Muffler looks like a stock mazda muffler, at least it's embossed with Mazda logo. Curious if previous owner maybe put a tune on it. At some point down the road I plan on getting versa tuner. Not trying to go crazy but maybe upgrade HPFP internals and tinker with tuning, i am assuming HPFP has not been replaced but maybe i will get lucky. Only way i found to confirm is to remove and inspect. But that is a project down the road once i sort out all the maintenance stuff first.
The rattle could be one of the pulleys. I would check the idler pulley as that is a common failure. The low tone with a little bit of a rough idle is also not uncommon. The previous owner could have either deleted resonators or added a test pipe or something along those lines. None of which will throw a cel. Unless it sounds like a full on misfire, I wouldn’t worry too much. If you’re able to get some pictures of your engine bay, there are plenty of people on here who can identify the what mods are on the car. Get a good picture of the downpipe if you can. And just to be safe, avoid doing pulls in 6th gear unless you are way up in the revs. Good luck and most importantly, enjoy the car!
Sorry for the VERY delayed response, apparently i don't have any alerts set. Update. Replaced alternator and when turning by hand you could here something clicking, pretty sure it's the alternator bearings, also battery was older then i thought. Replaced both alt and battery with red top optima and resolved! Still have alternator, maybe one day take and have it rebuilt for higher output for larger stereo.
Here is a few pics, like i mentioned nothing too crazy but some bolt on stuff, it gas aluminum splash plate and belstein struts
It has a K&N cold air intake, I added a 50/50 BOV but otherwise that is all i have done other then some maintenance.
