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Thread: Newly Rebuilt Engine Running Poorly

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    Default Newly Rebuilt Engine Running Poorly

    I have just finished rebuilding the bottom end of my Cx-7 2.3 DISI engine (hope it's okay to talk about a Cx-7 here). It won't run without applying some throttle and when it does run it is very loud and misfiring. It seems to even out a little at high rpm, but I'm afraid to push it too much. I suspect it is the timing. I am wondering if anyone has any other ideas, or can confirm that it is timing. I have checked the plugs and coils and they're good. I have attached a video of it running. Thanks for your ideas.

    Additional info on timing:
    I removed the valve cover to check the timing, and noticed that it is off somewhat. Notice in the attached pictures that the right cam lobe is aligned with the outside of the bolt while the left one sits more toward the centre with the #1 piston at TDC. Also, notice in the third picture that the #3 lobes on the intake side are aligned with the outside of the tappet while the #2 on the exhaust side overlaps the tappet. I expect these should open and close simultaneously.

    Is this enough to cause the issues that I have been having (see video)? Can I fix it by loosening the sprockets and rotating them, or do you think I will have to remove the cover and chain to re-set the chain in the proper place?




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    Default Re: Newly Rebuilt Engine Running Poorly


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    Default Re: Newly Rebuilt Engine Running Poorly

    Try the mazdaspeedforum.org . They have more information regarding the 2.3L Disi platform.

    .. while waiting for a more knowledgable guy to reply.

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    Default Re: Newly Rebuilt Engine Running Poorly

    Quote Originally Posted by Cjcoolen View Post
    Try the mazdaspeedforum.org . They have more information regarding the 2.3L Disi platform.

    .. while waiting for a more knowledgable guy to reply.

    thanks, I've posted there too. I realigned my timing today, so hopefully that did the trick and it will work better when put back together.

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    Default Re: Newly Rebuilt Engine Running Poorly

    Well, It has been a while, but I have a update.

    I removed the valve cover and was able to make small adjustments to my timing by loosening the exhaust cam sprocket and the harmonic balancer. It was off by a little because of the play in the cam alignment tool, but not much. I made sure it was perfect and put it back together, and it made no difference on how it ran.

    Since the timing was okay, I was brave enough to keep it running long enough to get a code, P2177 Fuel system too lean at off idle /ON. Research indicated that it should be fuel issues, low compression, o2 sensors, or a vacuum leak.

    Then I checked the compression and that was good, drained the old gas and put new gas in, cleaned the fuel filter (I couldn't buy one locally, and I'm not sure that you can buy them at all), and that didn't make a difference.

    Then I change the #1 O2 sensor, and still no difference.

    Then for about the 15th time I looked all over the engine bay for a wire connector or vacuum hose that I forgot to connect, and I found it.

    I noticed a hose hidden underneath the intake manifold that still had the clamp was pulled back toward the middle of the hose. After closer inspection I found out that the hose from the crankcase breather to the intake manifold wasn't even connected to the intake manifold. It is about 6 inches long, and hidden underneath the intake manifold in the dark, so I missed it each time I looked. I looked like it was in place unless you looked at it real close with a light.

    I connected the hose, and it runs like a charm.

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    Default Re: Newly Rebuilt Engine Running Poorly

    thanks for the update. Glad everything is now sorted.
    2010 Black Mazdaspeed 3 - Lightly modded

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    Default Re: Newly Rebuilt Engine Running Poorly

    thanks for the update. Glad your up and running. If you dont mind me asking did you assemble the engine yourself and if so did you do any machine work and where. Thanks

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