08 mazdaspeed 3 Stumble/ hesitates

Chowlwto

Chowlwto

Greenie N00B Member
My 08 speed3 stumbles and hesitates when I'm driving between 3-3500 rpm any idea what it could be, any feedback would help thanks.
 
Does the car throw CELs? Do you have any logs to post during the event? What were the most recent changes made to the car?
 
This is going to be really hard without a way to gather data from the car. do you know what tune in on the car? Just stock I assume?
 
I am wondering if this thing has a tune still on it from the old owner.

Does the car have a catless downpipe?

I guess step 1 is to clean the MAF sensor with MAF sensor spray. See if that helps.

You can look for a used Cobb AP or go VersaTuner and gets some datalogs. Any shop is gonna bill you $80 an hour to troubleshoot, so a tuning solution is going to help you a LOT.
 
Get Torque, or some kind of low cost monitoring solution ASAP. Better still get a tuning device like Raider said, because if you're going to have a modified car you need one. Returning it all to stock might be another option if it has stock tune.

Guys, if he did switch the fuel pressure sensor and it had stock tune, wouldn't the reported fuel pressure be scaled wrong? I'd think then the real fuel pressure would be way higher than reported and the ECU would effectively always be demanding as much pressure as could be provided by the HPFP. Would that even result in a motor that runs in any way normally?
e.g. in this post:
I believe the inj driver can shut down the injectors if rail pressure exceeds ~2500psi and missfires can begin around 2300psi but I have no idea what the conditions were. Missfires can be logged, just not with a DH or AP or really anything else except the dealer diag tool. I know Versatune is workin on adding it in.
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I'm still reading through that thread, so I really don't know where that all went, if it even went anywhere. Heck, somewhere in my mind I think I read that there was a choked-flow type orifice in the fuel system such that you won't get anything more flow no matter how much pressure you throw at it... and given that I never heard of this mod anymore I'm guessing the idea just fizzled when that or something similar was figured out.
 
Raider said:
My thought is to stock that out.
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Yeah, agreed.

OP can you verify that the air straightener is in you MSCAI? I don't know about the MS instructions but I think it's the same as the AEM and AEM's instructions show one.
 
Raider said:
Oh yeah. that old thing! Weren't they recalled though?
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I don't know. I haven't been around that long! But I'd have said to stock out the intake and see how it runs except the guy got the car used, so I'd bet he doesn't have the stock intake parts at all.

Looking around a bit further, Cobb issued a PDF service bulletin at one time that indicates in the acronym list that there is a MSCAI without straighteners and MSCAI2 with straighteners. I also saw some things that indicated there was a recall to add a splash shield, for one here.

OP, give us pictures of the intake system of the car, from as far forward as you can photograph (I assume the filter is hard to get a picture of down in the bumper) all the way to the turbo.
 
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