This happens to my car when I'm in stop and go traffic. The car is fully warmed up (having driven ~ 20 freeway miles prior to the back up) Typically, when I pulse the car, I put the big bar to the right of the ECO sign, so the gas engine kicks in, hold it for several seconds (traffic permitting) gather speed and then let off to glide. Every once in awhile, I can only hold the big bar to the right of the ECO bar for only a couple of seconds (if even that long...sometimes I just "goose" it in there and then back off) before I have to let off. when I "glide" the instant mileage doesn't climb back to 100 mpg, instead it stays around 50 mpg or less. Even as I lose speed, the instant MPG stays low. The front of the car is rumbling, so it seems that the engine is running, despite the car gliding. If I can give it a longer, sustained pulse, the event goes away. If I come to a complete stop, the event goes away. Any idea what is causing this?
Hi Codyroo, This is because the car is cold, and its running the engine rich to warm up the engine and catalytic converter. The 2010 handles this better, once its warmed up once, it stops doing this. Unlike the 2nd Gen, which would drop back in the warmup stages after cooling off during a glide. And then start running the engine again during glides again. Although, not neccassarily with enriched mixture (and the instantaneous MPG would still be above 100). It really takes a scangague or something with that capability to know what the car is doing in these stages, unfortantely....
I've wondered if it was the cooling too, but I don't know if I'm ready to fully accept the "engine is cold" theory on two accounts. 1) I've typically driven 20 miles to that point and the engine "should" be warmed up (freeway miles). 2) It only happens if the throttle is moved into the big band for a brief (split to 2 second) period. If I do it longer, I won't run into this issue. In other words, I can pulse for 4 seconds, glide. No issues. Pulse 1 second, glide - issues. Pulse 3 seconds, glide, no issues. It's very reproducible. I'm not saying you're wrong, I'm just not ready to fully buy into it, because my limited knowledge of how the car works doesn't agree with the observations. I realize that during my glides, the engine isn't running, thus is cooling down. But, even on the cool mornings here, after running the car for 3 minutes, I'll get the full 100 mpg on a glide. I would hope that after 20 minutes, the engine has enough thermal insulation to not cool down to the same temp as it was 2 minutes into operation.
Hmm, Welp, its not that then. The only other time I have seen the 3rd Gen do that is when the battery is at 2 or low in the 3 bar SOC. Its unfortunate that SOC gauge is not two decimals, so we could say, below 50% SOC, the engine will run to recharge the battery. But instead have to say well, when its low in the 3 bar SOC, which one cannot discriminate from other 3 bar SOC's....
SOC for my car is typically at the 6 bar range. It does seem to be SOC independant, because it will happen even with the car at 6 bars. I understand the engine will kick on when the car drops down to 2 bars (I've had that happen when the stop and go is REALLY bad), but not in this case. Interesting phenom.
I believe you were seeing the "idling check ceremony" in the S3 of Gen3 warming up stages. The "idling check ceremony" does not finished in a partial throttle. It requires an accelerator off gliding for several seconds. Ken@Japan
I'm also observing that the car will run the engine during a glide to keep the cabin warm. I can see ~50mpg, gliding downhill ~25mph. if i switch the climate control from "Auto" to "Off" the engine stops instantly.
In your case, the engine coolant temperature was less than 60C (140F), the engine was not hot (S2). In Codyroo's case, the engine was already hot enough (S3->S4). Ken@Japan
Then i guess i need to do some grille blocking, i have this happen entering a village, after 8 miles at 60mph.
