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Discussion Starter #1
My 2005 Elise has been stuttering lately, and I think I may have found a probably culprit. I would like to ask for help before acting, though: could someone pull their known-good MAF sensor out and get a clear image of the two elements inside of it? I would like to compare it to mine where one of the elements looks like it has corrosion/contamination on it. Before I purchase a new MAF sensor, I'd like some confirmation.

Thanks for your consideration,
-Obeisance

1267877
 

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Sorry I can't get to my MAF right now, but I'd be surprised if that little bit of corrosion does anything meaningful. How are you getting MAP though? Is it just calculated?
 

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I stuck a Bosch TMAP sensor on the vacuum flap port on the manifold, and push the data to the ecu from an arduino via CAN. the ecu also calculates map, and the value seems pretty close most of the time. i didn't look at the calculated map from these datalogs.. but i did record it. maybe it gets pulled down with the MAF signal, which it's based on.

if the maf sensor is not causing my car's stuttering I've gotta figure out what to look at next.
 

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I think comparing real and calculated MAF might offer a clue if you have sussed out how it is calculated. That sudden drop in calculated load does seems suspect though since, while it is decreasing, MAP doesn’t drop off nearly as sudden.
 

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It turns out that my problem has a dumb source: I found the flow vane loose in my aftermarket intake. I posit that the vane tumbled around upstream of the MAF sensor and prevented it from properly measuring air flow at certain times (this occurs in a sporadic manner when flow is high enough to move it around). When this occurs, the oxygen sensor can compensate for fueling target error, but the other engine controls (spark, valve advance, etc.) which are load driven still target erroneous values. On top of that, the vane may create turbulent flow conditions which lead to oscillatory behavior. I did not realize that the control system was this delicate. Once I removed the vane (rather than try to re-install it to a precarious friction fit), the problem went away.

As an aside, does anyone know if the MAF sensor is off-center in the OE intake?

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I had even tried substituting the known good MAF sensor from my Subaru, since it appeared functionally equivalent, but the problem persisted. This is shown in the rest of the plots attached to this post. As cyow5 pointed out, the contamination on the MAF (similar to the extent of what was on the Subaru MAF) does not seem to cause trouble.
 

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