Internal Combustion Motor Starts Immediately Upon Car Start Up

[ibjunior]

I just bought a 2006 Lexus RX400h with 55,000 miles. I've noticed that when I start it the battery starts to run it but almost immediately the internal combustion motor takes over as I leave the garage. I tried slowly driving around our neighborhood at low speed--20 MPH--on battery alone but the internal combustion motor always takes over even at a continuous low speed. Recall BLD re the power module hasn't been done yet and I plan to take it to the dealer ASAP. This recall doesn't appear to be directly related to my problem. I'm concerned whether this problem is covered by the 80,000 or 96,000 hybrid component warranty. I'd appreciate any thoughts.

[RX400h]

If your engine is cold, it will start in less than a minute after you turn the key. If your engine is fully warmed up, you should be able to pull away (very slowly) on battery power, alone.

[maseace]

You don't have a problem, that's how the hybrid system works. It's not a fully electric vehicle, unfortunately.

[ibjunior]

Phew..I get it. Many thanks guys. I missed that in the owners manual--if it's there. Perhaps that's why these forums exist...

[lemon]

If it stays running when warm, or seems to kick in with the slightest touch of the gas pedal, I'd seriously look into the ISC reset.

[eximius]

Because my two daily trips are short (20 to 30 minutes, but all in city) and separated by several hours -typical commuter-, I tend to get a fuel consumption profile which is continuosly decreasing, being the highest the initial 5 minutes (double than the average of the rest), due to combustion engine warming up its coolant.

Because I live in a mild weather area, and I always in an underground closed garage, such coolant is never cold, albeit not hot enough for it not to trigger the 'warm up' process.

The Prius has a heat isolated coolant reservoir, plus pump and 3-way valve (similar to Thermos) to maintain such liquid´s temperature for up to 3 days, but I am fraid that is not the case for the RX400h.

I am thinking that on skipping the warming up process in order to save fuel, without putting the engine into any risk, although probably the emissions would not be the minimum possible.

The way to do it would be to fool the engine coolant temperature sensor, making it to think it is warm when it is not.

Any feelings?

[maseace]

I am thinking that on skipping the warming up process in order to save fuel

No need to warp up at all before driving. Whenever you sit with the engine running you're getting 0 mpg! Better to warm up as you drive I say. An engine block heater may reduce or eliminate the warm-up time, but is usually only used in freezing climates.

I'm not sure how one would trick the engine temp sensor, but it probably would have unintended bad consequences in other areas.

[Jim Clark]

Our 2008 RX400h gas engine (ICE) is on most of the time, thats normal. It always comes on within 15-30 seconds of starting it when cold. Typically, the only times the ICE shuts down is when coasting or at a stop. Sometimes you can drive it slowly in a parking lot (or stop-and-go traffic) on electric only, if it's warmed up (that means oil, not coolant). It's not an electric car, it's a hybrid.

The RX400h does a respectable 24 mpg average, that's pretty good for a 4300# SUV. My old Jeep Grand Cherokee got 12 mpg, my little BMW 330Ci get's 18 mpg (all around town, it can get 23 mpg highway). Our Prius gets 50 mpg.

[eximius]

I own a RX400h and a Toyota Auris Hybrid Synergy Drive, and I am Chartered Industrial Engineer, so understand that I am qualified to comment on what follows.

The average fuel consumption listed on the catalogs are just that, average, so you have to take into account the type of use we make of the vehicle and the terrain by which we drive -and of the latter have not seen anything written -.

For example, the best performance compared to conventional cars is smooth terrain, in driving periods above 30 minutes, or shorter, but consecutive -and traffic jams, or with many stops, p. eg. due to traffic lights. And in temperate climates. And at moderate speeds, less than 50 mph.

That is, the best fuel consumption is most probably achieved by taxi drivers in big cities.

The worst can be found just in the opposite situations: Many climbs and descends, cold weather - even worse than the hot, including the overconsumption by A/C-, driving for less than 30 minutes separated by hours, because the ICE runs until the oil is hot, and that hurts the MPG average. And at high speeds, above 50 mph.

And above all, avoid palces with steep orography, as while climbing it consumes as a conventional car and in the descends the bad thing is not that you cannot recover the braking energy, a sit "overflows" the small battery, but that you do not have a way to slow down with the ICE, unlike even in a automatic, where you can shift to "2" or "1".

And no, the "B" is not enough. The solution would be to have a "B2" and "B1", to avoid eating up brakepads quite quickly!

So in small and steep islands, you will notice that hybrids are not purchased by the locals but instead rented by tourists willing to pay a premium or that might have been brought in from mailand.

It is a great technology, but if you do not use in its optimal conditions, you will be driving a technologically overloaded (and overpriced) car without obtaining back any economical nor environmental benefits.

[katzjamr]

also people forget that the engine must keep the catalytic converter heated to its optimum tempurature also for lower emissions

[maseace]

And no, the "B" is not enough. The solution would be to have a "B2" and "B1", to avoid eating up brakepads quite quickly!

The B mode doesn't eat up brake pads - per the manual, it's equivalent to downshifting in a normal transmission. The brake pads on Toyota/Lexus hybrids actually can last much longer because in most cases, the motor-generators provide the braking force when coasting or normal braking. The friction brakes are engaged during hard braking or when slowing to under 9 mph, where they trasition from regenerative mode to fricition brakes.

I agree with your other comments about mileage - where I live, I get better mpg on the highway than in city traffic, which is the opposite of the EPA average ratings. I usually get 22 mpg on my 10 mile work commute in the winter, 25 summer, and up to 30 on the highway on longer trips. My best tank was 32 mpg on a trip averaging 55 mph.