Verifying HCH is working correctly
Created July 11, 2007, at 11:33 am by jlallport
I'm at the dealer now because I noticed that my HCH does not seem to shift automatically when accelerating. No CVT lights, etc. But something doesn't seem right about a fuel efficient vehicle taking me to 6000 rpms withouth shifting - and I'm not trying to go up a big hill or pass a truck on the highway! Anybody else have that? The service managers says, "I'll have one of my guys drive it." "But without any codes, there's not much we can do."
When I combine this mild fact with the observation that the IMA battery always seems to get low, even after the car simply sits a while, I wonder if the car is behaving right.
Finally, the shrugging shoulders without a clear set of standards, facts, and obvious knowledge from the service staff makes me wonder how any of us nervous hybrid owners will get real information about what to expect from our cars.
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4 years ago
What year is your car?
What is its service history ?
Cheers;
MSantos
4 years ago
Sorry, I just read another of your posts and I see you got an HCH-II with low mileage.
If you are not happy with the answers/competency you have at the current dealership, may I suggest you visit another if possible?! Unfortunately, not all dealerships are managed with the values Honda often commands of them. Sad but true.
Anyhow, it would appear you have a CVT issue. This type of issue is very unusual in this generation of cars. There have been many Gen 2 HCH's checking in with much more than 50K miles and no CVT problems whatsoever.
- Have they (the dealership) tried to check for an available software update yet?
- Did they offer to change the H-ATF fluid yet?
- Have they tested the CVT speed sensor & circuit? They should've raised the car and performed the test with the front wheels spinning free for this test?
- They should also check the CVT clutch pressure control valve (while plugged to the HDS). If it's stuck then they'll surely see a P0796 code.
- When did you actually buy the vehicle?
- Finally, what is your driving regimen?
Cheers;
MSantos
4 years ago
thanks for the reply. they've done none of those things, but now I know to ask. Got the car on Dec 30, 06. Mileage hasn't been super, but driving regimen is: slight downhill in the morning 12 miles to work; slight uphill to return. creeps up to 39 or 40 mpg going down, back to 35-37 at home. a little heavy on the brake going down. When I take the car on a freeway commute, I get about 43-44.
4 years ago
So, with such knowledgable folks out there, here's the other annoying question giving me a furrowed brow when I drive: It is obvious that acceleration with inertia, such as speeding up or achieving velocity from rest, will use more fuel. Hence the drop in the mpg bar to almost zero at those times.
However, at the same time this is happening, the assist kicks in to help the engine. If the engine is getting help, why does the real time mpg drop so low? You'd think that was where the IMA is giving the greatest help.
It doesn't take much more than a lightweight engine and concientious driving to get that bar up to 80mpg at flat or downhill cruising. But just when you think the IMA is helping, the mpg bars drop down to nearly zero. So how much help is the IMA really giving? Or, how much is my 42mpg a product of "biofeedback" as I correct driving habits in keeping with my instrumentation versus a helping electric motor when I step on the gas?
4 years ago
Perhaps someone else may want to add to my response.
The IMA contribution to the act of propelling the vehicle is dependent on many factors, some of which you've already noticed on your own.
However easy it is to doubt that the IMA is doing much, let me assure you that an HCH-II without a working IMA is a "real dog" in terms of usability. It is slow and frustrating to drive in normal duty. If you like looking at graphs, let me introduce one below. If you look carefully you'll see what the typical contribution actually is in terms of power and torque (it is significant):
The other thing I would suggest is that you do not pay too much attention to the iFCD when the car is moving slower than 20 MPH. Yes, it will "indicate" very poor MPG but hopefully, when you get back to steady state cruising, those bad moments will be quickly nullified by the actual mileage you are going to get. Any of the existing hybrids will behave this way, even the Prius will have VERY bad FE, especially during its warm-up sequence.
IN other words don't worry too much about. In the end, this is a game of averages and whoever has the highest wins. ;)
Cheers;
MSantos
4 years ago
FYI, I had a problem with my CVT about a year ago that required the dealership to replace the pressure control valves. The CVT was stuck in low (20 mph with the engine revving at 6.5K rpm). But, I had fault codes and the amber engine symbol was flashing. Doesn't sound the same as your problem, by my dealer had to call the regional office for advice on what to do.
4 years ago
Indeed.
Issues with the CVT pressure control valves can be intermittent. That is why I suggested this to be one of the areas worth looking into.
In an intermittent failure the code generation has to be forcefully induced by the service person while the vehicle is "plugged in" - as I indicated above.
Cheers;
MSantos
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