WHAT IS THE CORRECT SPARK PLUG FOR MY 173CC - Mtd 19 In. 173 CC OHV 3-In-1

If you know the make and model of either the mower or the engine you will be able to search the online application catalogue of the brand of spark plug that is installed. Such catalogues list the recommended gap.

If you don't know these details, a rule of thumb setting that will be close enough to make most engines run is 0.025".
A few early magneto engines needed a closer gap of around 0.020"

Cindy, I believe this question was answered earlier , so this must be a duplicate post, if not let me know.
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Maybe the low oil level switch is bad. Disconnect the wire that goes to the low oil switch which is on the block of the engine and see if it runs longer. Make sure the oil level is to the full mark first.

Contact MTD if your manual doesn't cover this, or buy a shop manual.

Bad gas. Drain gas and refill with fresh gas with Stabil. Old oil. Drain oil fill with fresh 30w oil, 16-18oz. Clean air filter and spark plug.. Relpace air filter if dirty. Saving $$$ on this simple tune up is not intelligent.

follow this steps and fix it. GOD BLESS YOU

Service control cables:

1. Disconnect the spark plug cable for safety.
2. Remove the controller cover and loosen the locknuts.
3. Remove all slack from the cable, reposition the locknuts as needed, and tighten the locknuts.
4. Test the controller by moving it through the various positions and making sure it responds appropriately. If it doesn't, readjust it.
5. Reconnect the spark plug.

follow this steps and fix it. GOd bless you
Service control cables:

1. Disconnect the spark plug cable for safety.
2. Remove the controller cover and loosen the locknuts.
3. Remove all slack from the cable, reposition the locknuts as needed, and tighten the locknuts.
4. Test the controller by moving it through the various positions and making sure it responds appropriately. If it doesn't, readjust it.
5. Reconnect the spark plug.

Frst check the spark on coil remove spark plug leave wire connected see if it has spark if not check if ground on brake is releasing if it is replace coil if it has spark check fuel filter if it is ok clean and rebuild carburator.

You are not getting enough air. Clean the air filter and the spark plug.

Change the spark plug and the air filter. Also be sure the gas is new. If the gas has been in the mower all winter drain it out and put in fresh gas.