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Somewhere in one of these ECU threads someone who works at a dealership posted how every FR-S (like 5-8) they got on or before launch time (pre-production models?) showed this idle issue. I think Toyota/Subaru have known about this and got the failure rates down low enough to decide to launch the car. Also, a few months back technical documents were released showing details on the engine. IIRC mechanics on this forum were commenting on how unusually tight the tolerances were (and how long term, reliable forced induction would be a tall order/unfeasible)...
Subaru and Scion state it's purely software (ECU) related. A new ECU map was introduced mid-August yet there are VINs from after that time frame seeing the problem. I believe the new map reduces the likelihood but does not 100% eliminate the problem.
I believe this is a hardware/software interoperability issue [this is the engineer in me talking]. Tolerances are tight making this engine... touchy. You can only get the stacked tolerances of the oil journals, cams, casting, etc. to be so good yet always have a 1% +/- x-factor fail rate. Subaru/Scion PR wants you to believe it's purely software; in a way they can be right. When SW is controlling HW, there's no hard line separating which side the culprit lies. Components in the cam timing system would have to be revamped for all new parts/tolerances and would require retooling at engine assembly. Again, I believe they were aware early on ith the problematic prototypes and mitigated it from the hardware side the best they could before production rolled out. Now they leave it up to SW catch and clean up any straggling HW.
Some owners see symptoms after 8 miles, some after 6000, some never. Some only need an ECU reflash, some get their engine rebuilt and don't see it again, some continue to see it after 3+ returns to the shop. It's all over the map. Lack of consistency makes the problem impossible to isolate to one thing.
I have no conclusion here; just digesting what I've noticed in recent posts and posing the HW vs. SW question. On a slight tangent...
I remember when the redesigned 2000 Celica came out which had some similarities... new engine design, 100hp/liter, 11.5:1 high CR on premium fuel. It had a "lift" mechanism which activated a different set of cam lobes for a more aggressive cam timing profile. All triggered by oil pressure mechanically vs. electronically controlled VTEC/VVT-i which it also had. Just another moving part to go wrong... and it did. People were breaking their "lift" bolts and eventually revised bolts were made. Those people were in a tiny minority and many owners never had to change lift bolts, I believe. Anyway, this is all deja vu to me.
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