Small Engines (Lawn Mowers, etc.): Sputtering and stalling problem, briggs and stratton, octane level

Question
QUESTION: I have a Scotts Riding Lawn Mower [Model #S1742] with a 17HP Briggs and Stratton Intek engine.  It has been running fine until this evening when I was mowing.  After about 30 minutes, it began to "miss" and sputter, then eventually stalled.  I removed the air filter, shook it out, then replaced and it started up and ran fine.  After about 10 minutes, the sputtering and stalling happened again.  Again, after about a 10 minute wait, it started and ran fine, then the cycle continued.  I removed the spark plug and it had no fouling, but I cleaned it anyway.  I was mowing in a dusty area, but I do this all the time.  I don't think it's the air filter, but it seems to happen when the engine is warm, and I originally thought that it occured more often when going up hill, but I'm not sure now.  Any thoughts?   Thank you in advance for your assistance with this.

ANSWER: Henry:

How old is your fuel?  It sounds like you may have a vapor locking issue going on here.  What this means is the fuel actually starts to boil in the line before it reaches the carb, OR its just plain bad fuel. Maybe you have water in your fuel? Try getting fresh fuel from the pump.  Make sure the octane is at least 87.  Stay away from Ethanol blend greater then 10 percent until we get this problem resolved. Drain all your fuel from the tank and try it.

I would also put in a new Air Filter and fuel filter.  Good Luck!

Dave

---------- FOLLOW-UP ----------

QUESTION: The gas I put in was new, in fact I picked it up not 30 minutes before I started to mow.  This was what I thought of, since the mower had been running great and this was the only thing that I changed.  I got 93 octane gas [thinking that this would make things run better] can the octane level be too high for 4 cycle engines?  I am thinking it must be bad gas and/or dirt or water in the fuel.  I'll do what you suggested and see if this helps.  Thank you so much.

Answer
Great keep me informed.  When I test engines i sometimes test them with 110 octane AV Gas.. (Airplane Fuel)  so no your octane is not to high

Loosen your fuel cap to see if this resolves your problem as well.  You may have a tank venting problem.