The pre cat sensor worked fine when in idle (at the measurement ), and the post cat sensor gave 0.72~0.74 V (Is this high level because of high HC?). The lambda integrator was around 1.05, I think.Elevated HC with no CO often means the engine has a slight lean misfire, like from a vacuum leak. But if the car was running well in closed loop mode when the HC was measured, with the O2 sensors switching normally (at idle, the switching rate is slow, every 2-3 seconds), and the lambda integrators and adaptations in the normal range, then this rules out the usual problems like vacuum leaks IMO, and the two likely problems are a degraded cat (or cats), or an O2 sensor drifting and reporting good AFR when in fact it's not.
No codes at all. The all four O2 sensors are only four months old. They are all Bosch-made.How old are the O2 sensors? Any B2/B3 cats codes?
I did not know the ignition timing on all cylinders is locked at 15 deg at idle. Thanks. I have not measured them in driving around.Yes, the ignition timing on all cylinders is locked at 15 deg at idle, but it should change significantly while driving. Do you not see this?
The pic below is from the post #172. The exhaust camshaft angle do not change in consistent manner (around 4 deg which the DME commands). They think it could be caused by slacks of the chains. Of course they are not 100% certain. The solenoids could be the cause. They think mechanical part should be aligned before we say something about sensors and control.Re exhaust cam timing, it depends what you mean by randomly. The exhaust cam is the one that changes a lot during normal driving whereas it takes quite aggressive driving to change the intake cam timing.
Why are they dubious about the between-cam tensioners? They are pretty reliable.
What about long idle in congested traffic? As usual I had a lot of idling time (a lot of HC?) during the round trip.Re gas mileage, if the car is working normally in closed mode, maintaining the AFR at 14.7:1, then the only two factors that affect it are the ones that involve working in open loop mode, i.e. the warm-up enrichment time and the time spent driving aggressively.
I do not think the warm-up enrichment time matters because it take only a small part in the total driving time of nearly 3 hours. And the ambient temperature was around 10~12 C (50~54 F). I have to correct the average speed. It was more like 50/3 = 16 mph (not 30 mph).In your case, the second factor doesn't apply, and since your car now appears to be running well in closed loop, the gas mileage is affected only by the warm-up enrichment time. This is very dependent on ambient temperature so naturally as the weather cools down, gas consumption increases. This may be what you are seeing. 15 mpg doesn't seem to bad to me, especially if it's US gallons.
And of course, the t/s has to work well.
1 Gal = 3.78541 L (by my hp calculator). I believe this is the US gal.
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