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Thread: 07 CX7 serious knocking noise under acceleration

  1. #1
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    Thumbs down 07 CX7 serious knocking noise under acceleration

    So, my CX7 is playing up again!
    I bought the car brand new in 2007 and since then despite regular 4000 mile oil changes with full synthetic and following the recommended service guide, it has gone through 3 turbos and a brand new factory engine, A/C compressor and transfer case. (All covered under warranty)
    Last week, we noticed a knocking sound at 3K RPM but it disappeared very quickly as you accelerated. I guessed it was a heat shield or cover vibrating as it was not possible to replicate just by revving the engine.
    Today the check engine light came on and the knocking got significantly louder and is now throughout the rev range. If you let off the throttle or accelerate very slowly, it does not knock consistently but under power it sounds like a can with a couple of large ball bearings in it being shaken!
    I took it to the dealer who didn't have time to look at it, the service guy who writes up the jobs thought it may be either a low end rod knock, the VVT failing or maybe a valve issue.
    The car makes power and sounds perfect at idle.
    They suggested I authorize 1/2 a days labor and they would try to figure it out but said Mazda would likely not cover all of the bill if any at all.
    To add insult to injury, I went to see the sales guy for a price to trade it in against a new CX5 GT, the reply, $4 to $5K IF it had no issues but as is, "about "$2K" I paid $27K for it new so $4K equals $23K depreciation in 6 years, that's pretty poor considering I just sold a basic Ford Focus with 123K miles for $2700!
    Fuck that, I took it to a local a local mechanic and asked him to investigate....
    I see a new vehicle in my future once the CX7 is repaired but after all the issues I have had, I doubt I will ever consider another Mazda.
    "Zoom Zoom" more like "Clunk Clunk"
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  2. #2
    Booga Booga? phunky.buddha's Avatar

    2009 Mazda5 Sport

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    Does it do the same on a different tank of gas? Maybe you got a bad tank?

  3. #3
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    Pretty sure it's not gas, also was ding it a week ago but only at 3k rpm and now the noise is throughout the rev range under power.
    Any one else had serious mechanical issues??
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  4. #4
    'Turbo Turtle' lildisco's Avatar

    08 CX7 AWD GT w/Nav, 06 6i Sports Sedan

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    these things require more than just oil changes. You need to let the turbo cool practically every time you drive you car, (highway driving, heavy foot, basically anything that makes it go into boost), the EGR valve gets excessively dirty and needs to be cleaned reguarly. The A/C compressor had a TSB & i believe there was something with the transfer case too. Luckily, they were all covered under warranty.

    It sounds as though something wasn't done properly during the installation of the 'new' engine. I wonder if it was a engine off a totaled car, instead of a new crate engine. They will do that, but with 3 turbo's bad, i think there's something else going on. I've had the vent kit installed on my CX7 nearly 20,000 miles ago & over 2 years ago without any issues. I know it will eventually need to be replaced, but i purchased the Mazda Certified Used Extended warranty when i purchased the car used over 2 years ago.

    Nothing against you, but from what i can gather, i notice a lot of people never have driven a turbo'd car before. Therefore, they don't know the steps involved into making the turbo/engine/car last. Premium Fuel is a absolute MUST in these engines, especially since yours is a 2007 & doesn't allow for any other grade in it's factory tune. There's different grades of Premium. I can get 93 Octane around here & i usually stick with that. I've noticed a difference from 91 to 93 octane fuel. The best stations i've found around my area are Shell & Sunoco. Both give me the best performance & fuel economy. Cleaning the EGR can also make a world of difference for these cars.

    I'm looking into getting a JBR Oil Catch Can kit for this car for that reason. Less blow by & junk getting in the motor and causing problems. I know i shouldn't have too or need to, but it's like that extra level of protection.
    Cooper Red Mica 2008 CX7 AWD GT w/Nav
    K&N Drop In, Stock Air Box Mod, HKS BOV, Silver Star Turn Signals, LED Fog Lights, Xtec Hi-Beam Lights, Tinted Tail Lights, ETS TMIC, CS Boost Pipes, RX8 Wheels wrapped wtih Yokohama AVID ENVigors
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  5. #5
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    Quote Originally Posted by lildisco View Post
    these things require more than just oil changes. You need to let the turbo cool practically every time you drive you car, (highway driving, heavy foot, basically anything that makes it go into boost), the EGR valve gets excessively dirty and needs to be cleaned reguarly. The A/C compressor had a TSB & i believe there was something with the transfer case too. Luckily, they were all covered under warranty.

    It sounds as though something wasn't done properly during the installation of the 'new' engine. I wonder if it was a engine off a totaled car, instead of a new crate engine. They will do that, but with 3 turbo's bad, i think there's something else going on. I've had the vent kit installed on my CX7 nearly 20,000 miles ago & over 2 years ago without any issues. I know it will eventually need to be replaced, but i purchased the Mazda Certified Used Extended warranty when i purchased the car used over 2 years ago.

    Nothing against you, but from what i can gather, i notice a lot of people never have driven a turbo'd car before. Therefore, they don't know the steps involved into making the turbo/engine/car last. Premium Fuel is a absolute MUST in these engines, especially since yours is a 2007 & doesn't allow for any other grade in it's factory tune. There's different grades of Premium. I can get 93 Octane around here & i usually stick with that. I've noticed a difference from 91 to 93 octane fuel. The best stations i've found around my area are Shell & Sunoco. Both give me the best performance & fuel economy. Cleaning the EGR can also make a world of difference for these cars.

    I'm looking into getting a JBR Oil Catch Can kit for this car for that reason. Less blow by & junk getting in the motor and causing problems. I know i shouldn't have too or need to, but it's like that extra level of protection.
    I have many years of experience with turbos, both on motorcycles and cars. The car is driven by my wife and always has been, she is in her mid 40's.
    The current problem is not turbo related, it definitely is something serious inside the engine, lifter, valve or crank by the sound of it.
    I can't find anyone to touch if for less than $1000 and as per my original post, Mazda don't seem to want to know..
    What was interesting was the service tech said he had seen literally a hundred guys like me with serious CX7 motor problems in his time. Hardly confidence inspiring!
    Don't know what the next move is, basically it is tough shit, fix it or literally give it away, either option is not something I can afford...
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  6. #6
    'Turbo Turtle' lildisco's Avatar

    08 CX7 AWD GT w/Nav, 06 6i Sports Sedan

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    I've had to get on my wife about driving the car and letting it cool down and so forth. Your mazda tech saying he's seen a lo of cx7's with motor problems kinda goes a long with what i was saying. Most people don't know how to drive a turbo'd vehicle or takes proper care of the car.

    With your engine knocking or making noise, leads me to think something happened, spun bearing, VVT issues, etc. Did you ever figure out if they put in a new crate engine or used engine from a low mileage cx7?

    My experiences with Mazda USA customer service has been completely different. Never really had any issue with them honestly. I guess it's all in how you present yourself to them?
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  7. #7
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    I was told the engine was a new from the crate one, so it should last more than 30k miles!
    I have called around and no matter how I slice it, everyone is saying $750 to $1000 just to figure it out!
    I have had no issues with customer service, just no luck with the car!
    I spoke to them today, they agreed it was not typical to have such a large amount of serious issues but they are refusing to do anything this time!
    Going to try and trade it tomorrow, I really like the CX-5 but I will never buy another Mazda after this experience.
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  8. #8
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    Traded it today for an Acura MDX. My wife was sad to see it go as she loved its looks and ride but after so many issues, I am happy to see the back of it.
    It will take a lot to convince me ever to buy another Mazda!
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