By on April 11, 2012

 

TTAC commentator Kitzler writes:

Hi Sajeev,

Quick question everybody ignores: I personally do not like racing a cold engine. My last two cars, a Dodge and a Lexus, both had automatic transmissions. When the engine was cold, Summer or Winter, worse in Winter, you had to rev the engine to 3000. before it would shift properly. Worse, the automatic would not shift into top gear until the engine was lukewarm, a couple of miles. Now here is the clincher, as the cars got older, the couple miles became three. What gives?

Appreciate an answer about racing a cold engine and why the damn automatic won’t shift properly, thanks.

Sajeev answers:

First off, this problem is multiplied when you are crazy enough to install a high-stall torque converter in your Lincoln Mark VIII. It’s bad enough with a stock stall speed unit, but add the looseness of a drag-racing worthy fanbox in your gearbox and you need even more throttle and more wait time before the car behaves normally. But you didn’t come here to read that, did ya?

This is normal for darn near any car with electronic fuel injection and an electronically controlled gearbox. Both are needed, as transmission behavior depends on the reading from the engine’s coolant temperature sensor. Yup, engine coolant is a fine bellwether to the future of your engine and transmission’s programming parameters. Let’s face it, a cold engine is not ideal for any driving condition. You want the motor to warm up ASAP.

Cold fluids are bad for performance, tailpipe emissions, and longevity of your car’s power train. A vehicle needs to be loaded up to get the fluids up to operating temperature ASAP, so the computer does just that. And once the coolant temperature looks peachy, the engine/transmission oil follows suit. Revving the engine to 3000rpm is a good idea, as opposed to stewing in “friction-filled” cold fluid at idle or trying to circulate this thick/cold stuff at 6000 rpm.

And here’s my point: you are NOT racing a cold engine from what you stated, you are doing exactly what is needed.

As to why this behavior is worse as cars age, well, that’s harder to say. Perhaps the coolant temperature sensor isn’t reading accurately: its internal resistance from cold to warm (to hot) is no longer linear. Perhaps old fluid has a viscosity problem that throws a monkey wrench into the system. Or perhaps it gets harder to overcome “the shivers” as we all get older. Which is why we all gotta roll the moment we wake up in the morning!

Send your queries to sajeev@thetruthaboutcars.com. Spare no details and ask for a speedy resolution if you’re in a hurry.

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37 Comments on “Piston Slap: Shake, Shivers…so Roll!...”


  • avatar
    espressoBMW

    My BMW owner’s manual specifically states to not let the car warm-up by letting it idle. Instructions are to start it and get going.

    • 0 avatar
      aristurtle

      Same thing for my motorcycle. Apparently oil doesn’t circulate properly when it’s stopped and idling; it should be moving to warm up.

      • 0 avatar
        200k-min

        My ’99 Honda owners manual says the same….and I imagine any vehicle made post 1986.

        Every winter I laugh when I see my neighbors idiling their cars for 10…20…30 minutes so it’s “warm.” Waste of gasoline.

        I find that in my now 13 year old vehicle the vents are blowing HOT air before I have gone a mile in sub zero temps.

    • 0 avatar
      early

      Turbo charged engines require 10-30 seconds of idle to get oil pressure up to the turbo components before sprinting off and spinning the turbo.

  • avatar
    Terry

    This high rpm cold/last shifting is an emission-control strategy designed to heat up the catalytic converters quickly, cutting down on cold start emissions., nothing more. 02 sensors only operate when heated to 600 degreesF, so the quicker the engine gets into a feedback loop, the quicker the engine gets under computer control, and the lower the emissions.

  • avatar
    Landcrusher

    This is a classic example of following rules you don’t understand. We all do it because we are engaged in so many things we can’t know them all, but when it comes to engines it seems we are extra resistant to change. Its smart that the guy asked. Most people are so stuck on what the learned before they will assume the manual is wrong.

    Even plane owners do this sort of thing. There was an old saw about engine settings being taught to new pilots even recently that goes back to radial engines! The operators manual would recommend efficient settings that would not be used because generations old rules that never applied to small piston planes were still being passed down.

    • 0 avatar

      I sense someone who cruises LOP here.

      • 0 avatar
        Landcrusher

        I always cruise LOP, and that’s another myth that survived forever. My Ovation’s manual recommends LOP settings. It made it to 2000 hours and had I not quit flying regularly, my A&P says it would hav gone to 2400 easy. I also ignored shock cooling nonsense and saved a huge amount of fuel whenever I could descend without ATC forcing me to the tree tops or their convenience. I stopped talking about it around airports because I found there were plenty of pilots who classified you as one level better than child molester if you didn’t go along with what they “knew” was “best”. Most still think I just got lucky like a guy who takes off into hurricane and lives.

  • avatar
    Silent Ricochet

    My car’s engine feels like absolute garbage until it hits operating temperature at 195F. Literally, The engine feel’s very rough and while the power is there, I feel like I’m hurting it unless I keep the revs below 3k. My owner’s manual states that 10 seconds of idle time when first starting the car is sufficient to keeping the longevity of my engine, although it also states to not “race” the engine until operating temperature is reached. I feel that, on a 20 degree day, 10 Seconds of idle is definitely not enough. No matter the season, unless I’m late to work, I let my car idle for 2-3 minutes, longer in the winter. It may be a waste of gas, but at least m engine will last longer. Whether or not it’s true, I’m not sure, but at least I feel better about it.

  • avatar
    SherbornSean

    Would an engine block heater be an easy fix?

  • avatar
    Educator(of teachers)Dan

    I do let vehicles warm up but I’m trying to cut it to about 5 to 10 min instead of the 30 min my father used to do on cold mornings to his work car. Even my fiances Vibe with the 5 speed manual isn’t happy on winter mornings until a couple of gear changes throw the fluid around the box and things start to warm up.

    • 0 avatar
      supersleuth

      If you have to park outside, as I do, sometimes there’s no choice in the winter, because on certain mornings it’s impossible to keep the windshield clear of ice until there’s some warm air available. Driving blind could be a lot worse for the car than idling. ;)

  • avatar
    ciddyguy

    Unless there is ice on my windshield, I just get in, put it into gear and go, even in the winter as I have no choice but to park on the street and I know that most cars built since the mid 80′s don’t require you to let it warm up before you go anywhere.

    Now when there is ice, I’ll crank up the engine, hit defrost, high fan and hit the rear defroster and grab the scraper and scrape, once cleared, I get in and go but that’s the ONLY warmup I do, simply to clear the windshield and nothing more.

    By the time I get 2 blocks or so, I begin to feel heat coming from the dash vents. I know if the thermostat is going when it takes longer for the heat to reach the cabin or the temp gauge takes longer to move above C and at least in my old Ford Ranger, it’ll idle unevenly by revving up and down when the thermostat actually goes, giving me ample notification that something’s amiss.

  • avatar
    DenverMike

    Your car is delaying shifts because it’s running crappy in the morning and you’re squeezing the go pedal harder to make it go. In terms of throttle position, the computer thinks you’re street racing. It’ll shift on time when you can drive it without your foot to the floor.

    Nevermind what the “experts” tell you. Always, always warm it up if you’re remotely concerned about engine life.

    • 0 avatar
      JuniperBug

      Maybe if you’re driving something from 1981.

      On anything built in the last 20 years or so, what’s actually happening is the computer is delaying shifts, as well as preventing the converter from locking up, to intentionally get the engine and transmission up to temp faster. 3,000 RPM is far from “street racing” territory, unless you’re driving a diesel tractor.

      I agree that warming it up is important, but the method to warm up a car is to drive it gently, not idle it at a speed where your oil pressure is minimal and you’re wasting gas going nowhere. This advice goes back at least to my ’92 Jetta’s owner’s manual. But then there will always be uninformed “experts” who think they know how a car works better than the people who engineered and built it.

      • 0 avatar
        DenverMike

        Auto makers want max MPG, not max engine life, so yeah they want you to get going. A car’s computer will compensate for driving away cold, but is it good for an engine long term or even short term? Why drive a car gently until it warms when you can idle it for 10 or 15 min and keep up with traffic or stomp on it to merge if need be? I don’t take an on ramp ’till I’m ready to rock.

        Kitzler mentioned his problem had gotten worse over time. Does a computer also compensate for a car’s age/miles?

      • 0 avatar
        golden2husky

        I drive all my cars till really old age, like 150K to 250K and well over a decade in years. 4 cylinders to 8′s. I let oil pressure stabilize and then drive moderately for the first few miles. I have never had any engine failures at all, except a head gasket on a Chrysler 2.2 at 250K plus. Only the oldest of them all (92 Sable) has long warm ups and that was only to clear the window. But Vulcans never die. So I see no reason to idle for 10 minutes at all….

      • 0 avatar
        Moparman426W

        I believe it was sometime in the late 40′s when the automakers stopped recommending warmups. During extremely cold weather I will let mine run for around 30 seconds before popping it into gear to let the fluid circulate through the trans and the oil is well circulated through the engine by that time. I accelerate moderately until the engine and trans are up to normal temp.
        Letting an engine sit there and run to warm it up increases wear and tear on everything.
        While it’s sitting there running there is friction on all of the parts, just like if the vehicle was going down the road. The pistons are moving, the valves are opening/closing, etc. the water pump and all of the other accessories are turning, the fuel pump is running, etc. That is why vehicles with highway miles last much longer than city driven vehicles, because they don’t spend half their time idling at traffic lights, etc. That is also why many companies have engine hour meters on their trucks.
        If you let your vehicle idle for, say, 10 minutes in the morning before heading to work, and 10 minutes before coming home that adds up to 2 hours worth of wear and tear over a 5 day period, just think of the figure it would add up to over a year’s time.

    • 0 avatar
      DenverMike

      You can climb into a cold cabin and get on the road, shivering and shaking and struggling to see out icy windows and moving at a snails pace while I just jump into a toasty warm cab and wave as I pass. Not that you’ll notice me what with all the wiping of the windows and windshield wipers going full blast. If you’ve got a heated garage, more power to you, but you’re saving what, 15 cents by not warmng it up before you drive off? BTW, what does that heated garage run ya?

      Accelerating is also known as pulling a load and puts way more wear on an engine than idling. Do you think top fuel dragster engines wear out by idling up to the lights or going down the track? But then accelerating (even gently or moderately) a cold engine just accelerates that wear.

      Highway driven cars show less engine wear because they avoided stop & go traffic and not so much the idling at lights. It’s not the ‘stop’ that wears on an engine, it’s all that ‘go’. Highway driven cars are basically idling down the highway.

      • 0 avatar
        Moparman426W

        I had to stop laughing enough to even type. I’m not even going to bother with this one. (still laughing)

      • 0 avatar
        DenverMike

        Nah, go ahead, take your best shot. Sounds like you’re fresh out of ammo…

      • 0 avatar
        Moparman426W

        Ok, I will explain a couple of things. Yes it is true that an engine is barely turning above idle while going down the highway.
        But the car is also traveling along with it, as in covering miles, that is one reason that a highway driven vehicle will go ‘more miles” than a car sitting idling at a traffic light, the city driven car is not covering any distance while it’s engine is running.
        While the car is sitting there in drive with the brakes applied there is slippage in the torque converter, which builds up heat in the transmission, causing wear. Wear is also caused by the shifting of the trans as the car accelerates because there is slippage in the clutches during a shift.
        Normal acceleration is not what causes wear in a street driven car’s engine. A dragster makes thousands of horsepower and turns at insane rpm’s and reaches 300 plus mph in like 3. something seconds nowadays, that is why a dragster engine has to be rebuilt regularly.
        And no, I don’t park my truck in the garage, my wife’s car takes up one side and the new yorker takes up the other.

    • 0 avatar
      DenverMike

      No, you’re pinning most of city driving wear & tear on idling instead of bring a car up to speed again and again, possibly a dozen times per mile as opposed to once every 20 miles (or what have you) on the highway. That’s ignorant.

      The trans fluid in the torque converter is slipping, not actual clutches in it or in the trans while idling. It’s that fluid that gets pushed against the fins inside the torque converter (above idle) that connects to the trans input shaft. Only cars or trucks that tow need to keep tabs on trans temps. That’s what overheats a trans other than racing. Or should taxi drivers in NYC start installing trans temp guages for sitting at lights? That’s ignorant.

  • avatar
    DC Bruce

    I had a Toyota Previa that would not shift into top gear at 50 mph (the programmed setting under less than hard acceleration) until the engine was warmed up. I assumed that the reason for this was driveability issues — even with a fuel injected engine — when the engine was cold.

    BMW and, perhaps Honda on certain high-revving engines, has a variable redline on the tach which is set lower when the engine is cold.

    But avoiding an upshift that leaves the engine pulling at only 2,000 rpm seems to me a decent strategy for any cold engine, even if that keeps engine speed in the lower gear at 3,000 rpm.

    And, if your car is outside at night where temperatures regularly fall into the single digits or lower (in F), an engine block heater might be a worthwhile investment in engine longevity.

    The other thing about idling a cold engine for an extended period of time is that this is the slowest way to warm an engine up and it prolongs the period during which the engine is running a very rich mixture. Some of that extra gasoline blows by the piston rings and finds it way into the lube oil, which is definitely not a good thing.

    The reason people idled cold engines in the old days is that automatic chokes (to enrich a cold engine) were tempermental beasts which often leaned out an engine too early, resulting in stalling, bucking and all kinds of unpleasant behavior. The problem with a cold carburetted engine is that the cold metal surfaces of the intake manifold condensed the gasoline in the gas/air mixture coming from the carburettor creating an excessively lean mixture going into the cylinders. So, one of the things the warm up did was warm up the intake manifold. In-line engines with external manifolds were particularly afflicted with this problem. V-block engines usually had shorter manifold passages and since the manifold was a casting on top of the engine block, it was warmed up more quickly than the in-line engine’s manifold, which was outside of the engine. Big six-cylinder engines with a single carburetor and a long intake manifold were particularly susceptible to this problem.

    • 0 avatar
      JuniperBug

      This man knows what he’s talking about.

      The only reasons I ever found to idle the engine longer than it took to buckle up and get ready to drive was when it was -10 or colder outside. Firstly, it was unpleasant driving with the cabin and windows that cold, and secondly the oil in my manual transmission was so thick at that temperature that shifting was all but impossible. Letting the shafts spin in neutral for a few minutes stirred it up enough to get things going. The alternative was to drive around for the first few miles without leaving second gear, but that wasn’t overly pleasant, especially while shivering waiting for the coolant to get up to temp. A block heater would have undoubtedly helped.

  • avatar
    tankinbeans

    This kind of brings up a question I’ve had since I got my car. My car will idle at about 2000 rpm for about 35 seconds upon start up and then will idle down to 1500 rpm. Is it wise to wait for it to idle down before setting off. Also, during the winter I will generally keep it one gear lower than normal until the car warms up. For instance if I’m going 35 I’ll keep it in 4th until it warms. Does the routine change for manuals over autos?

  • avatar
    kitzler

    Thanks for the reply Sajeev, I now own an Audi and the engine does want to initially go past 2000 rpm when cold, but not 3000, plus the eight speed tranny quickly shifts up to seven, the eighth gear is for freeway driving and when the engine has been running a few minutes.

    But this Audi behaves totally better than either the Lexus or Dodge, we’ll see what happens as the car ages, thanks again Sajeev

    • 0 avatar
      JuniperBug

      Different engines behave differently because of a variety of different factors. What’s normal for one engine isn’t necessarily the same for another. As an example, during my time as a valet at an outdoor airport parking lot, I found that Toyota Matrixs (Matrices?) and their Pontiac twins cold-idled considerably higher than most other cars. If memory serves, it was around 1,800 RPM or so. My Honda motorcycle (late model, EFI controlled with limited closed-loop capability) also idled around 2,000 RPM during the first minute or so of a cold-weather start. Considering the 12,000 RPM redline on that bad boy, I found that reasonable. The 5,000 RPM tickover on choke for the first few seconds on my carburated ’89 Ninja was a bit more unsettling, but still altogether normal on that model of bike.

  • avatar
    A Caving Ape

    My friends always think I’m crazy for doing a few laps of the ski resort parking lot before heading down the mountain. Otherwise it never warms up!

  • avatar
    kitzler

    that is a good question Denvermike, yeah, does a car computer use time, age of the car or miles driven, as a parameter. I don’t see how a sensor could make a difference over time, a sensor either works or does not work.

  • avatar
    zoomzoom91

    you get heat after two blocks? that’s awesome, i want what you drive. our acadia literally takes forever to get warm air blowing, it sucks in the winter. explorer before that was considerably better.

  • avatar
    Moparman426W

    No, I’m certainly not out of ammo, trust me. It’s just that some of the things that you said were so ignorant that it’s not worth wasting my time trying to explain such simple things.

    • 0 avatar
      DenverMike

      Like what’s ignorant? You’re being really vague now. Just give one example. Two words are that hard?

    • 0 avatar
      SimonAlberta

      Frankly, both of you have said some things that make perfect sense and you have also both spouted some ridiculous nonsense.

      I can’t work out if you are both clever guys who are getting a bit carried away by the arguing or if you are both idiots who don’t know what you are talking about.

      Somewhat entertaining I must say, so please keep it going fellas.

      • 0 avatar
        Moparman426W

        You two are the idiots who have no idea what you are talking about. The only thing he said that made any sense was the part about towing. But the conversation in the beginning wasn’t about towing, it was about city driving VS highway driving.
        I suggest you both find someone that works on automatic transmissions and have them show you all of the internal parts and explain to you how an automatic operates, then you will see what I was talking about. Have them show you an older pre electronic unit, because they use less parts and will be simpler for you to see everything. Modern automatics work the same way, the only differences being they have more gears, more parts and are shifted electronically. By the way I rebuilt my first transmission in 1979 when I was 16 years old, it was a turbo 350.

  • avatar
    ekaftan

    If your engine is not warming up as fast as it did, replace the thermostat. Most fail open as they age.


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