prr

I have decided to spend more than just 10-15 seconds warming up the car in my driveway. I have a Toyota minivan that gives me lifter knock when I go up to 2500-3000 RPMS (40 mph) a minute after pulling out of the driveway, and when I wait 60 seconds in the driveway, I don't get that sound at all.

Now I know some folks advise not just a matter of time, but to simply wait for the loud idle to die down. I warmed up my 98 Civic this morning, took about 30-40 seconds max (walked 20 feet to front door, locked two doors, then walked back to the car), and the idle was still high. When I started the civic yesterday afternoon, about 2 hours after driving it for about 15 miles, a good 10 miles of freeway driving, it started up immediately at low idle. Does this make sense?


Anyways, I want to know if I should simply count to 60, or would there be a definite advantage to waiting all the way till the high idle speed drops.

mcnoople

I am curious about your toyota van with lifter knock. I don't remember any toyota engines with hydraulic valve train. I know the old "MZ" series of V6 engine had spacer buckets that had to be measured and changed to adjust lash. If it is a 3.5 it isn't lifter noise it is piston slap and lots of them do that.

Temperature at start makes all the difference when it comes to warmup time. Cold start on a 30* day is completely different from a cold start on a 60* day. What were the temps on the mornings in question.

prr

I got the phrase "lifter knock" from a friend who knows cars, but doesn't drive Toyotas. All i can say is that when I've driven in the mornings after warming up the car, I don't hear that sound.



The morning temps have been around 40 degrees (at the time of driving) for several months now.

Colin42

Stone cold engine, idle will be high for a bit and then settle down after a little while. That's normal.

Normal, engine was still warm.

Hope this helps.

As for the toyota something might be a little loose fitting that tightens up once it gets warm

prr

My question is---would there be any reason for me to idle all the way to the point where the RPMs drop, or should I just keep doing what I've been doing---idling while I count off a minute or so, and then drive away, even though the idle was still high.

ezone

That's not lifters.
Cold knock in the Toyota is probably piston slap, it goes away as the aluminum pistons warm up and expand to fit their holes. Not unusual at all.

I see no reason to wait at all, fast idle or not.

In fuel injected cars I usually don't wait for anything (because they usually run great cold without being finicky or temperamental at all), as soon as the engine is running on its own I put it into gear just as fast as I can move my hand from the key to the shifter.
In the dead of winter (as long as the engine doesn't make strange noises or anything else unusual) I still do this in my own car, unless I wish to warm it up to get some heater output before I go anywhere.

In customers cars I MIGHT wait a few seconds just to make mental evaluations of everything I can take in, noting anything unusual or unexpected.

====

Back when I had cars with a carburetor, I tried to keep them in good tune so they weren't real balky at running from cold.

My truck, on the other hand, has a carb with the choke disabled (on purpose!) so it's not easy to make it go right off the bat. I have to pamper the throttle a minute to get it warmed up enough just to stay running on its own. (this also prevents most other people from being able to get it started or drive it)

prr

Not gonna argue with you here, but I do want to understand why you said what you did. One of my cars has, ok, not lifter knock, but piston slap, when it is run before being warmed up.

Isn't preventing this, reason enough to warm up the car a bit before driving away? Or are you saying that this isn't going to hurt anything? I can't help but think that metal on metal contact, that can be prevented, should be prevented.

ezone

I would have no qualms driving it like that. You might, but I personally don't.

Loading the engine (driving) makes it heat up faster than just sitting still idling, thus reducing the length of time the pistons remain cold and shrunken.


In the case of the Toyota with slap: As mcnoople said, it's typical, it's expected, and it's not really hurting anything. That engine has probably been doing it for a long time already and it's gonna do it until its dying day, and it's not bloody likely to die from a piston problem directly caused by the slap.



If you want to know WHY they have piston slap, it's because the pistons are machined to be a specific size at operating temperature.
Because the pistons are made of aluminum, they grow and shrink a large amount between stone cold and operating temperature.
If they machined the pistons big enough to be super quiet when cold, they would expand when hot and either scuff (damage) the cylinder walls from too little clearance, or seize completely in the bores and it wouldn't be able to run.


Cold piston is shrunken and fits loosely in the cylinder bore = lots of noise as the piston rocks in the bore
Hot piston is now full correct size and fits correctly in cylinder = very little rocking = much less noise.

Some engines do it louder than others, some piston designs are more prone than other designs too.

Many Hondas do it (whether anyone driving notices or not).

One manufacturer I worked with years ago (Mazda) had us replacing pistons in certain engines for the slap noise issue, the redesigned pistons had teflon coated skirts to reduce the intensity of the noise.
FWIW on those engines I had apart, I never saw cylinder wall damage from the slap.
(BTW I checked the date on this repair bulletin, it was issued over 25 years ago...and I'm feeling really damn old now)



Copy/paste of Mazdas statement regarding other engines with the cold engine piston slap noise:

Mazda Motor Corporation has engineered and developed its piston engines to meet a wide variety of operaing conditions while deliveries excellent fuel economy and performance. Mazda makes extensive use of modern metal alloys to meet weight and emission requirements.

As a result of these varied and exacting requirements and materials, a number of components in the engine may, during initial start-up and warm-up, expand at different rates with resulting changes in some clearances during this period. These design criteria result in minor noises which your 929 and MPV customers may have noted.


Mazda wishes Mazda's Servicing Dealers to assure its owners that these minor noises will not, in any way, affect the reliability, functioning or long term durability of their V-6 engine.


We have experienced no failures related to this notice condition with this type of Mazda V-6 engine in the subject vehicles during our extensive laboratory and real-world test.



Copy/paste of Hondas statement about cold engine noise:

Cold Start Knock
To some degree, cold start knock (piston slap) is a normal characteristic on 4-stroke gasoline engines. It happens when the engine is cold (piston-to-cylinder clearance at its greatest, and most of the oil has drained back into the pan). As the engine warms up, the knock should quickly diminish, usually within 2 to 3 minutes.


I wonder if mcnoople can provide a statement from Toyota about their noise?

prr

Wow. A very thorough answer. Appreciate that.