DF40 Idle Issues

[Pot Hole]

My 2002 DF40 has a miss at idle at low speed that I can't seem to figure out. I'm running an inline fuel filter (changed regularly) and premium gas with ethanol treatment. It cranks fine, and when I give it gas in neutral it revs up OK, but for some reason when I put it in gear and start to head out, it will miss (sputter) every 5-10 seconds. When I open her up, she runs like a scalded dog, so WOT is fine - no misses at all. It is a tiller model and I do not have a tachometer on it right now.

I've run some Lucas fuel injector cleaner through it and some Sea Foam, but the problem persists. There are no engine warning beeps indicating an internal problem, and the motor probably has about 100-150 hours on it. It's basically been a garage queen for the past 10 years, but I've had her out quite a bit here lately. The miss is not keeping me from running her, it's just aggravating.

Any ideas on where else to check? I've heard there may be a couple inline filters I need to check/replace and possibly a clogged VST tank? I wouldn't think it would be a clogged injector given how well she runs at WOT, but you folks may think otherwise.

[artdf175]

I don't see any replies - I don't know much about the 40 hp
But most operate much the same
First question is fuel Did you dump old fuel and replace with all fresh fuel?
This is probably the number one item for these engines not to run well
Is your fuel filter a fuel/ water seperator type? Very important if you have to run ethanol fuel and by the way It's not required to run premium fuel
You may want to drain the VST and check the fuel filter inside of it
Is there any crud in the small inline filter that comes before the low pressure fuel pump?
They usually sputter a some point if there is a clogged air vent in the fuel tank
Doesn't sound like on your case but worth checking
Let us know what you find
Art

[Pot Hole]

Art,

I've run at least 3-4 tanks of fuel through this engine over the past couple of months, so the fuel I'm using should be pretty fresh and yes my filter is a fuel/water separator. The VST (and it's internal filter) is something I need to check on once I find out where it is and how to access it.
My fuel tank is an older style with the air adjustment screw on the top of the tank. I've made sure it was open and not vapor locking.

If it was a carburetor motor, I would swear it was a clogged low speed idle jet, but it is not, which has me baffled.

[Pot Hole]

You may want to drain the VST and check the fuel filter inside of it

Is there any crud in the small inline filter that comes before the low pressure fuel pump?

Art

Is there a easily accessible diagram of this motor showing me where the VST and the inline filter prior to the low pressure fuel pump is located?

[artdf175]

I am not sure where a diagram might be other than the full service manual
$80-90 from either this web site or Brownspoint
However it is just following the fuel line
The fuel line, if like some other models, comes from the fuel connection on the front of the engine goes down the port side before attaching to the low pressure pump - look a fuel line prior to this pump
VST is on the starboard front on my engine Just follow the fuel line from the low pressure pump
If you look at the parts page "purchase parts" at top of forum page you can god the part and see a blown up image