Does anyone know about how long after a cold (40-50F) start does the engine stay at 1500 rpm? The reason I ask is on our old car after about 10 or 12 seconds the idle speed slows from 1500 down to 1200 rpm and we put the car in gear and go. On the RDX we've waited at least 30 or 40 seconds and the idle speed still hasn't begun to slow down.

 

very normal, cars now days manage themselves, you will notice when it goes in gear it will lower, once the engine is warmed up it will idle more normally, you don’t need to wait for the idle to lower, in fact idling is when higher wear occurs, the worst point of wear is when you first start the engine, but the engine is working to get itself to operating temp so it will operate at max efficiency

 

I'd say normal is 45 s to 1 minute. From what I've read, there's no need to wait until the engine is warm before driving, but I'm oldschool so I generally give it the extra 30 seconds.

 

Thanks for that, that was what I was curious about. It seems like it would be a little easier on the drivetrain to wait until the idle comes down a bit before shifting into gear but I don't see us waiting that long as a general practice.

 

Its not a bad idea to let your car run for 30seconds before driving. I try doing it myself when I dont forget.

 

I've idled all my cars for a few mins before taking off in winter months. More so to get the cabin temp up a little before I get in. Absolutely no engine issues whatsoever on any of my vehicles. It's more important to take it easy while driving around when the oil temps are cold as opposed to whether or not idling to "warm the car up" is good/bad. I see people who tout that the practice of idling is bad for the car and then hop in their cars in 20*F and accelerate away like they're testing 0-60 times. Regardless of temps, I don't take off until the infotainment loads. It's usually about the same amount of time it takes for me to buck up, turn the auto stop/start off and then turn the crash mitigation off.

 

My wife's Subaru idles near 2k when cold. I hate putting the cold tranny in gear at that rpm but what is the option? I don't believe in long warm-up idling. It's like the engine hates the transmission. But, considering how annoying that cvt is, I can understand the sibling resentment.

 

I do notice that 3rd gen RDX has higher idle RPMs at initial start than my previous 1st gen RDX. Maybe thats how all Honda DI engines idle now? Or higher RPM at idle during initial start is unique to 2.0L turbo engine?

 

Likely emissions related. Getting the temp up quickly.

 

Good thought. It's not like a DI engine is gonna stall when you open the choke, like my clunky snowblower. But the catalytic converters aren't effective until they get heated up by engine exhaust.

But really, there's no harm in driving the car while it warms up, and if you're worried your tender parts will freeze the heater gets going faster when the engine is working harder. Besides, the thing has electric seat warmers. No bean burritos required.

When it's cold enough for a northerner to say "uff da, dat's friggin cold" the transmission will shift sluggishly until it gets warmed up, but idling won't do much about that anyway.

 

This is one of those personal opinion topics, but I agree with the school of thought that promotes driving moderately when cold as more effective than idling longer. I idle 20-30 secs and easy does it we go. I live off a 2-lane road that allows that, but others may have a different situation.

 

I also always let my cars warm up before taking off on cold or warm weather, atleast until the rpm goes down to 1000 or until I see the temp gauge start to populate. I also have an 2003 element with 203k and no issues with the engine.

 

The K24 in that Element is legendary for being just about as reliable as an automotive gasoline engine can be. Had an Element myself. 200k is routinely mid-life with nothing but regular oil changes and occasional valve adjustments. Honda at its best.

Warm up philosophy certainly won't matter there.

 

My '19 idles at 1500 rpm when cold started (not freezing temps... 50-60 F etc), and when I back out of my garage, often without waiting any more time than it takes to buckle my seat belt and push the R button..the car seems to vibrate...a lot. As soon as I get past the garage door, I brake to a stop on the driveway, hit the Homelink button to close the door, and find that the car is certainly not feeling like a Luxury or Premium brand. (My wife's new 2020 CRV seems much "calmer" and not vibrating so much under same scenario). I forgot to notice what RPM the CRV idles at upon startup. I don't get to drive it very often.

I asked the dealer about this at my last visit, and they said "they all do this". However, they gave me a '19 RDX Tech as a loaner, and it idled at 1300 rpm immediately, under the same exact conditions. Hmmm??? ...and it didn't vibrate the same way. So I guess they DON'T all do this.

I guess I'll have to time it to see how long it takes to settle down to 1300 RPM.

Maybe it is outside temp controlled? But I think mine has always done this...

Rambling on as I get tired of "shelter in place" and look at more of the same. SIGH

Be safe everyone!

 

My 2020 Tech idles at around 1,500 when started. It typically takes less than a minute for it to drop down close to normal. I nearly always wait for the RPM to drop before moving. If I'm in a hurry and immediately put it in reverse, it is very rough and jerky.

My wife's 2017 Advance with a V6 starts at less than 1,000rpm and backs out of the garage very nicely.

 

mine is smooth and doesn’t shake, there was a TSB related to Kinda what your having

http://www.urvi.net/forumfiles/SB/B18-063.PDF

 

As is our habit, we're only waiting 10-15 seconds before putting the car in reverse while the rpm is still at 1500rpm. At no time though has it ever vibrated or been rough or jerky. After backing out, the rpm's flare up for an instant as the car shifts from reverse to drive but unless I'm looking at the tach you would never know it as it is very smooth.

 

Does it make a booming noise when you shift ?

 

I don't think I get a "booming", more like you had your foot on the brake and were trying to accelerate after a stop light change...which is exactly what is happening. I stop on the driveway while the garage door is closing...(it's a short driveway, maybe 25-30 feet long, with a slight downhill to the street) this is where I feel the high idle trying to move the car while the brake is applied. The car all seems to "vibrate". Maybe it is a booming....but not necessarily when I shift to Drive. I will also see if I get that flair up that GW208 mentioned, the next time I go out. (who knows when that will be!)

I will have to show my service adviser the TSB that Dereileak posted. Service advisor has been at this dealership for a long time, but he doesn't seem to really care about the customer's concerns. I have only seen him a few times, as I have only owned an Acura a bit longer than one year.

 

No, I don't notice anything like that at all, it is very quiet. If it wasn't for the tach I wouldn't even be aware of the fast idle. It's not an issue really, I'm just used to our old car that would begin to slow the cold idle after a few moments and kind of expected this car to be the same.

 

The fast idle is programed in as a drivability and emissions item. Cold engines need a richer mixture due to condensation of fuel on the head and cylinder walls but if you put in more fuel you need more air to go with it. When we had carburetors we had a choke with an attached fast idle cam that was made to compensate for the added fuel using a "fast idle" cam that provided the idle stop when cold. Those of you who remember driving these vehicles may remember that if you let them sit and idle without touching the throttle they would warm up, the choke plates would open but the car would not come off the high idle cam on the choke until you hit the gas pedal to lift up the adjusting screw off the steps of the fast idle cam. When we went to fuel injection this job was taken over by the IAC (Idle Air Control). The IAC was a plunger that was moved by a stepper motor. If opened a bypass channel that allowed air to bypass the closed throttle plates to give the car more air while cold. This action was all programmed into the ECM based on the coolant temperature reported to the ECM. On a cold start up the engine coolant temperature sensor has the greatest authority over fuel and idle speed. When cold the ECM will give an extra long pulse width and put more air in to go with all that extra fuel, which gives your engine a faster idle. As for how long the vehicle will stay on fast idle depends upon the values programed into the engine control module. Since the ECT (temp sensor) had the greatest range of authority on a cold start up the temperature of the coolant will normally cause the speed to drop sooner. .Today I watched my tach on a cold start up and once the engine was running I could sit and watch the RPM slowly come down after the start up. But, it was "warmer" out, in the 70's so the programing wasn't going to call for too long a time on "fast idle".
As for cold start ups: General feeling of professionals based on empirical knowledge shows that the best approach is to start the engine, give it a few seconds to pump the oil around and then drive off, in a moderate fashion, which will let the engine warm up much quicker and not stress out the engine. Don't instantly slam it into gear nor flog it while its still cold! Just use common sense and drive it moderately while its warming up and it will last a long time.

 

My 2007 Honda would use shifter movement to change idle mode. As soon as the shifter moved slightly from Park, the idle would quickly drop; this seemed like a good design. It's typical now to have a higher revving engine engage a stopped transmission, often when very cold. I assume this is accounted for in engineering, but still seems less than ideal from an owner experience standpoint.

 

When I shift into D or R when cold the transmission does a very smooth and gradual shift into gear. It never "thumps" into gear or jerks. Of course I only shift into gear when the engine is at idle speed. I have seen people actually have their foot on the gas (in a hurry to go I guess) as they shift into gear and then wonder why its not smooth. I have never tried this on my RDX but seen it all too often on other vehicles.

Modern vehicles with electronically controlled throttles and transmissions, especially with variable displacement transmission pumps, tend to shift into gear much smoother than older vehicles. While some detest electronic throttles they really do improve drivability and longevity of the drive train and reduce emissions.

 

Agree. It's also likely this sort of discussion is confined to owner forums where people tend to be more aware of their vehicle's function. I know I focus way too much on this sort of thing. I imagine the overwhelming majority of owners never give idle speed a second, or even first thought.

 

I spend a lot of money for this car and just like enjoying it. After over four decades in the industry solving every one else's problems this car is a fun toy to play with. I enjoy learning all the features and playing with them just for entertainment. If I just wanted transportation I would drive my wife's cute little Honda Fit all the time.