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Vacuum oddities
Over the past week or so, I have noticed a slightly unstable idle when previously the idle was completely solid around 760-780 rpm. The 'unstable' idle will creep upwards very slightly but it doesn't creep over 1000rpm. I also notice on my OBD2 reading of vacuum pressure that it is a bit higher than normal; ~25in/HG compared to a previous ~22in/HG.
I would normally say this is a vacuum leak, ICV needs a cleaning, MAF cleaning, TB clean etc. The HIGHER than normal vacuum confuses me, but I had wanted to clean the intake assembly anyways. So I did all of that very thoroughly, in addition to inspecting all vacuum hoses for leaks and did not find any. So far its storybook vacuum gremlin (except for higher vacuum???). I quickly checked the oil cap for signs of AOS failing and it seems the same as always, easy to take off, but engine will stumble slightly after a few seconds of having it off.
I then got a pending P1126 (one of the cylinder banks at maximum richness at idle speed), which would explain the slightly unstable idle, and would also make me think small vacuum leak even more than I previously did. I drove ~200 miles this weekend and the pending code never activated the CEL. After cleaning all of the above, I cleared the code and drove ~80 miles and nothing. The slightly unstable idle remains however (so I assume the code will return).
After cleaning everything(ICV was a bit stuck), car runs better and my OBD2 display of 'engine load' (not sure how this is calculated; it is somewhat REAL however because with the AC on at idle, load goes to 1.6%) has dropped from a consistent 1.2% (warmed up, california-hot day) at idle to a 0.8% at idle under same circumstances.
Higher vacuum tells me AOS is starting to fail (J tube was dry inside), but does a beginning-to-fail AOS cause a P1126/all of the other symptoms? I want to invest my cookies into a more thorough vac leak search but not sure this makes sense either.
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