Well, to eliminate this as a problem, try cleaning out the fuel tank cap vent. The cap vent being stopped up (or partly so) can cause symptoms like this, especially if you begin mowing with the tank completely full. A good way to check this would be to run the tractor long enough for it to stall and die, then remove and retighten the tank cap. If the cap vent is clogged, loosening the cap will break the vacuum that develops when fuel is burned. Because you notice a difference between full throttle operation and 3/4 throttle operation, I would say your cap is not completely clogged, but very near clogged. Anyhow, this is cheap and easy to try.

Hi Frank. Problems like this are among the toughest to diagnose. The first thing to understand is the set of criteria that you have when the problem occured is great for attempting to reproduce the problem, but not to try and say that "X", "Y", or "Z" is the cause. There are a few more pieces of information that need to be known, and thats where the professional technicians scan tool and experience come into play. Question, once this act's up does the car restart immeadiately? Does it occur every time you come to a stop once it starts acting up? Or, will it only do it once, and then maybe not do it again for weeks? Does the check engine light come on BEFORE the car actually stops? If you take the distributor cap off, can you see a light dusty film inside it? (This BTW is NOT an actual diagnosis of "the/your car's" problem, but is a sign of a typical problem that "might" be causing your problem. There would be no direct way to know other than watch it for an extended period of time where the problem does not happen anymore.) If you anticipate the problem occuring can you gently hold the idle speed high enough (stopping with two feet, one on the gas and one on the brake) and prevent the car from stalling? How much time would go by before the car stalls a second time once it does it the first time? What I would have to do is be able to drive this with test equipment hooked up, so that I could narrow down to a praticular system what is causing the stall. Currently the list would include, but in fact not be limited to: Distributor pick-ups. Ignitor module. Coil. Fuel pump. Ignition switch. Computer. Wiring. EGR, if equipped. Vacuum leak. Idle speed system. (IAC, Throttle body adjustment, TPS) Fuel control system. (O2 sensors, Injectors, Fuel pressure, computer sensors) Many times I'll get a customer to drive a random issue car like this until they recreate the conditions that cause the stall. That way I get to see the car only while it's happening. Sometimes people leave a car with me for weeks so that I can drive it repeatedly and eventually (hopefully) get to experience and diagnose the fault. I would not suggest, nor would I guess any parts to throw at the car just from your description.

Egr valve can stick open and cause motor to stall. Old cars used vacuum to operate egr valve. Newer cars have electric solenoid operated egr valves. Not sure what ur car has but all can stick. Not to say ur ignition issue is main problem or just 1 of ur issues.

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