Do You Throttle All The Way Down Before Turning Off The Engine?

[patrick_g]

Is there a downside to throttling down to idle before shutting down? Needed or not it doesn't hurt and could help. Letting it idle for a little cool down before shutting off the ignition is IMHO not going to hurt and likely will be kinder and gentler to the engine.

Oh, and by the way... Hi, I'm Patrick. New guy on this forum and fairly new to ride-on mowers. (previously just used brush hog o Kubota compact tractor 39 HP at PTO.)

 

[GrassFire]

Is there a downside to throttling down to idle before shutting down? Needed or not it doesn't hurt and could help. Letting it idle for a little cool down before shutting off the ignition is IMHO not going to hurt and likely will be kinder and gentler to the engine.

Oh, and by the way... Hi, I'm Patrick. New guy on this forum and fairly new to ride-on mowers. (previously just used brush hog o Kubota compact tractor 39 HP at PTO.)

I know some claim the engine is actually hotter when idled down because the ventilation has been reduced. Supposedly if you shut it off at full throttle, you're at maximum cooling so it doesn't have the chance to build heat by reducing the rpm's. Seems odd but I have read it before.

I started in 1999. I have always idled down before shutting off and I start at idle speed. I engage my PTO at idle and disengage at idle, also. Never had an engine issue to date. But I also sell my equipment with less than 1000 hours.

 

[Ronno6]

If I remember correctly, my Hustler manual says to engage PTO at 2/3 throttle or so,
and idle down prior to disengaging.
Seems like shutting off the engine at idle is a logical step afterwards.

 

[efred]

I was told by a tractor mechanic (I'm a farmer) to run engine at about 1/3 throttle, not 1/2, not bottom idle; at about 1/3 idle, the engine will cool down most efficiently (enough fan cooling, not making a lot of heat), and then shutting off after about a minute works best.

For my mower, a '98 CC 2165, letting it idle at about 1/3 throttle for about a minute will shut off fine. If I shut it off at full throttle, it will backfire. My best friend, who has an '06 Dixon, has to shut his off at full throttle, or it will backfire at anything less. So, in general, follow your model's manual for shutdown.

 

[rrodger9]

Per my owner's manual, I put my CV25s at half throttle before shutting it off. This is to avoid backfiring. I also throttle it down before engaging the pto clutch. This is to help preserve the deck belt and clutch.

 

[CalgaryPT]

Absolutely, at least 30 seconds at low idle before shutting down. I can't recall hearing or seeing anyone press their vehicle gas pedal to the floor and holding it before switching the the key to off.

LOL. Agreed.

But my teenager wouldn't. Apparently"cool" people rev their engines before turning them off.

No wonder I am a social failure. This forum really is helpful.

 

[huck18]

my ferris 21hp kawasaki mower wants to be shut down at full throttle or it will backfire when I shut it down after lowering the the throttle, called the dealership and was told to shut it down at full throttle.

 

[patrick_g]

There is an obvious benefit to letting an engine cool down some before shut down. Heat stored in high temp metal components of the engine tends to "fry" the lubricating oil a little at each full temp shutdown. A little cool down before shut down reduces that significantly and helps preserve the high tech additives in the oil to the benefit of engine's longevity. Unfortunately some folks experience backfiring if they attempt a low RPM shutdown. Still there are concerns regarding unburned fuel if engines are shut down at high throttle settings.

I have a plethora of small gasoline engines in such devices as generators, self propelled DR string mower/trimmer, a Weed Eater string trimmer, 5-6 chain saws, and on and on. It is my practice to run a device at a low throttle setting for cool down and then turn off the fuel and let the engine die from fuel starvation. No excess fuel washing lubrication off the piston and cylinder and no fuel left in the carb to cause varnish and plug things up if the device isn't run for a while.

My 46 inch swath Cub Cadet ride-on mower is happy to be shut off after a cool down at reduced RPM and does not backfire. If backfire was a problem for me I would consider shutting the fuel off and letting the engine run at cool down RPM until it ran out of fuel.

A cool down period will not double your engine life but it will tend to increase it.

 

[broo]

My operator manual for Toro Timecutter tells me that engine startup, turn off, and both PTO engaging and disengaging should all be done at full throttle.

Makes you wonder why they bothered installing a throttle control at all.

I still idle it a bit before turning it off out of habit.

 

[mhavanti]

Its all those folks that kill engines at full throttle that engine re-manufacturers and for that matter, engine manufacturers love. Full throttle shut off does a few things to your engine. Allows a nice lean condition as the engine is slowing once the ignition is switched off as long as the anti-backfire solenoid is working. For those that either don't have a working solenoid or the solenoid has been disabled by the plunger shortened, there will be a full rich mode. Now, full rich does help cool the engine I'll give you that. Fuel that isn't burnt also cleans the lubricating facilities from the valve guide, cylinder, piston skirt and rings. The fuel that gets past the rings goes where?

We can go on and on from a machine shop perspective and thank you for continuing to shut down with WOT. lmbo. At any length, if the manufacturer is telling you to shut down WOT, then you bought from the wrong manufacturer. Brand loyalty used to come from longevity of products, ease of use, manufacturer truth, etc.

What has the world come to?

Max