Hi All,

I started noticing that on my 2007 TCH, when accelerating, it achieves high RPM's as expected (like when passing on the freeway). However, when I ease off the accelerator, the ICE very slowly upshifts to bring the RPM down. This happens much slower then usual. I tried searching to see if anyone has experienced this but either no one has, or I wasn't using the proper search terms. The closest I found was someone on the HCH forum here: https://www.greenhybrid.com/discuss/...pm-range-8958/

Just reaching out to the community to see what you guys/gals think. I have 145k miles on it.

Thanks!

 

While browsing the forums, I ran across this.. https://www.greenhybrid.com/discuss/...32/#post242462

"The elevated rpm after accelerations is the fuel, sounds like the butterfly valve in the throttle body is sticking. Sound good but I don't know if the '07 TCH even has one. Google should know.. You might pull the air intake tube off the metal intake and look inside. I had a '94 Corolla that stuck and I saw a butterfly operated by a servo. I used a little carb cleaner to clean out any dark deposits and that fixed the sticking problem. Ask youtube you may learn more and find a better cleaner than I used."

Worth checking out?

 

There is no "upshifting" as they TCH doesn't have any gears to shift. If you are talking about the engine throttling back slowly due to the throttle body being dirty, yes that can happen but they usually "stick" and release quickly.

Note!!!! If you decide to clean the throttle body, DO NOT use carb cleaner. Use a cleaner designed for a throttle body as they are a little milder and will not remove the factory coating on the inside of the throttle body.

More than likely, everything is working as it should be and it is just the ECU reacting to the gas you have, temps, engine loads and your driving style.

 

ditto. No gears, no shifts.

 

Thanks for your input GeorgiaHybrid. I understand it's a eCVT, but couldnt think of another way to say what you did about the engine throttling back slowly. It may be working as normal but I haven't experienced this behavior in the past 6 years. I'll continue to monitor it and see what happens.

 

I have a TCH 2009 that behaves like yours since it was new. As previous members have mentioned above, TCH has not traditional gears to downshift/upshift. Computer controls the ICE rpm by changing continuously the MG1 rpm for a given car speed (a given MG2 rpm) to put the ICE rpm to the most efficient point.
From my perspective this is a glitch in the software. Computer is not able to take the decision while you keep gas pedal pressed hard (difficult to understand if you really need power to merge or just normal acceleration). We help the computer to make the decision by showing our intention with easing the gas pedal. This is similar with automatic transmissions for the same condition (keep pressing hard the gas pedal), computer is not able to take decision to upshift.

 

While the TCH doesn't have traditional gears - it still performs shifts in the form of changing the ratio between MG1 and ICE to modulate the efficiency and torque output of the ICE. For those with a scanguage or the torque app with OBD2 reader, you can see this with cruise control on when going up a hill. You will see the ICE RPM increase with MG1 increasing as well to achieve the higher torque output.

I believe what the OP is saying, that when going from an application of the throttle with torque (i.e. acceleration) back to cruising (holding a steady speed) the drop of this ratio, to cruising conditions and effectively having the engine holding at a cruising efficiency is taking longer.

 

How do you know your RPM is not coming down after passing? Are you hearing the engine rev by ear? Or?

The hybrid responds to power demands differently than a conventional vehicle due to the e-CVT and the sophisticated control system. It tries to keep the RPM and torque on the red line shown in the graph below. The more power you need the further up the red line it climbs. Initially it just increases torque, but as more significant power is needed it mainly increases rpm. So as you suspect when you pass rpm should go up and then come immediately back down again.

If you have accurate rpm measurement and are sure it has changed something must be wrong. Not sure how the control system would respond to a sticking throttle valve. I guess it would cut back on fuel to run very lean and reduce torque, but rpm may hang up? Not sure. The other possibility is that the control system is gone wrong, but that is much less likely than a sticking throttle valve, especially considering your mileage. I would initially go the throttle body cleaner route to see if that helps.