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I have a 2020 cub cadet xt2 lx46,with just over 100 hours on it. Several times now it gets sluggish and almost stalls on me after cutting grass for about an hour. It starts to run unevenly and if I stop and turn the blades off it recovers briefly. If I continue to mow, it will stall out.

If I shut it off and let it sit (cool down?) for 10 minutes or so, it starts up and I can continue mowing.

At first I thought it might be a fuel issue, but I replaced the fuel filter, and it's happened with different tanks of gas (I only use gasoline without ethanol). I also recently replaced the air filter. I'm going to pull the spark plugs and probably replace them.

What do you think is the problem, and what should I check?

I think you have a very small (for now) crack in your plug insulator(s). Everything is fine until the plug grows enough from heat to open that crack and cause the spark to jump out of the insulator to ground. I've seen this happen with automotive plugs many times.

Joed756 said:

I think you have a very small (for now) crack in your plug insulator(s). Everything is fine until the plug grows enough from heat to open that crack and cause the spark to jump out of the insulator to ground. I've seen this happen with automotive plugs many times.

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Hmm. By "plug insulator" do you mean the spark plug cable? I've never heard of a plug insulator.

Spark plugs have 2 insulating regions
The white bit under the electrode cap you put the spark cap on and the cone on the inside that surrounds the centre electrode
If the bit inside the engine cracks then the spark will go through the crack rather than jump across the gap
Electricity is even lazier than I am and always goes along the easiest path
A new plug is only a couple of dollars and if it makes no difference then you have a spare sitting on the shelf for the next service .
Usually your symptoms are due to a partially blocked fuel line or blocked fuel line outlet in the tank.
However that usually only becomes a problem after a few years as it take a while for the crud to build up inside
However I have seen things in tanks like used condoms . plastic bags, the old price tag from the shop ( obviously annoyed the sales person ) .
Then their is over helpful small children who will put all sorts of stuff in a fuel tank to "help daddy"

OK. Now I understand. I'm going to go ahead and replace both spark plugs when I get home on Thursday. Thanks for the tip.

bertsmobile1 said:

Spark plugs have 2 insulating regions
The white bit under the electrode cap you put the spark cap on and the cone on the inside that surrounds the centre electrode
If the bit inside the engine cracks then the spark will go through the crack rather than jump across the gap
Electricity is even lazier than I am and always goes along the easiest path
A new plug is only a couple of dollars and if it makes no difference then you have a spare sitting on the shelf for the next service .
Usually your symptoms are due to a partially blocked fuel line or blocked fuel line outlet in the tank.
However that usually only becomes a problem after a few years as it take a while for the crud to build up inside
However I have seen things in tanks like used condoms . plastic bags, the old price tag from the shop ( obviously annoyed the sales person ) .
Then their is over helpful small children who will put all sorts of stuff in a fuel tank to "help daddy"

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Man is that aggravating trying to track down a crack in a plug. LOL @ Electricity being lazier than you or me. True!
I found a rag floating inside a gas tank on an old 8N Ford Tractor once. Start it up fine, run it about 10 or 15 minutes
and then it would start to starve out and die. Shut it off for 15 minutes, take a break, start it back up and same thing. And Welcome to the LMF cubby!

Checking Back in. I replaced both spark plugs and have used the mower three times and it seems to be running fine. So, even though the spark plugs weren't scheduled to be replaced yet due to hours, I believe new ones fixed the issue.

I ended up buying the more expensive E3 brand plugs with the forked electrode. They are supposed to be better quality, so I spent the extra few bucks. Thanks for everyone's help!

Here is a couple examples what Bert referred to:

The plug on the left actually fell apart while I was disassembling the plug. The areas marks are cracks and there is no way anyone can see these except disassemble as I did. Plus this is the area where the resistor lays.

Believe or not the engine was only giving minor spark issues. Replaced them with some new NGK-2460 plugs.

bertsmobile1 said:

... I have seen things in tanks like used condoms . plastic bags, the old price tag from the shop ( obviously annoyed the sales person ) .
Then their is over helpful small children who will put all sorts of stuff in a fuel tank to "help daddy"

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I had a 72, Formula Firebird that would start bogging and stalling when the gas got low. I strongly suspected some junk in my gas tank. the gas station pulled the tank and found what appeared to be a paper bag inside. from the rolling and sloshing much of it had turned into a perfectly round ball of paper . I suspect that this happened at the factory..

I bought a Cub LT1046 last year from a fellow who was convinced it had engine issues. He told me he believed it needed a "ring job." The symptoms he described sounded much like those in the original post here. He told me it was "fouling plugs," and he showed me one of the "fouled" plugs. It wasn't fouled. In fact, it looked quite normal.

After I went through the machine -- which was in pristine condition, clean enough to eat off of, with only about 200 hours on it -- I sold it to a church friend. I had found absolutely nothing wrong with it, and even thought about keeping it.

A couple weeks later, my friend called and said the engine was dying out under load, but would start up again if he let it sit for a while. That is, BTW, the classic symptom of a fuel feed problem. I brought it back to the shop for service.

I replaced the fuel pump, the fuel lines, the fuel filter. I went through the carburetor. I did all the routine stuff to chase away the fuel-flow boogeyman. Nothing changed.

Out of desperation, I snatched off the seat and the fender pan and pulled the fuel tank off. Inside the tank I found a small bit of red plastic that had lodged in the fuel outlet. The plastic, which did NOT block the fuel, had gathered tiny bits of grass and dirt over time, and those bits had formed a sort of plug. That was the problem. Once I cleaned the tank and put everything back together, all was perfect.

mechanizm said:

I had a 72, Formula Firebird that would start bogging and stalling when the gas got low. I strongly suspected some junk in my gas tank. the gas station pulled the tank and found what appeared to be a paper bag inside. from the rolling and sloshing much of it had turned into a perfectly round ball of paper . I suspect that this happened at the factory..

Click to expand...

I had a '71 LTD with a similar problem. I had replaced the fuel pump and the notorious Ford fuel filter -- the one that screwed into the front of the carburetor -- to no avail.

I went to the local parts store, the one where the guys behind the counter actually worked on stuff and knew what the hell they were talking about. While I was standing in line to talk to my buddy Dave (who always had the best advice), I listened to a guy describing a problem with his Ford Country Squire wagon that sounded exactly like my problem. Dave told the guy that Ford puts a filter on the pickup tube inside the gas tank on that model. I knew instantly that my problem was the same.

I jacked up the car, crawled underneath, and opened up the front of the tank, where the fuel gauge float and the pickup line go in. I pulled the business out, and sure enough, there was a bag-type screen filter on the end of the pickup tube. I slid that filter off the tube and threw it away. Then I put the whole business back together, and I never had a fuel feed problem with that car again.