Power fails when mower deck in use

John Deere LX 188
New problem that appeared after lunch. Mowed about 1 Ac before lunch, everything good. After lunch, engine declines in RPMs when mower deck is cutting grass. If engaged but wheels not moving forward mower spins up nicely. But as I move forward RPMs decline unless forward speed kept very very slow.

I have cleaned plugs, changed fuel filter, changed gas. Blades brand new. I also checked mower deck for string or weeds binding. Cleaned underside of deck in case of interference. Nothing there.

Temps high 50's, sunny. Grass moderate, about 1-1/2 to 2" to cut.

It could be fuel related may have picked up some debris in fuel tank or electric PTO problem or possibly a battery problem. I would try new spark plugs first.

Pull one plug wire off. Try and start the engine if engine does not start then you have no spark to the other side.

Carscw said:

Pull one plug wire off. Try and start the engine if engine does not start then you have no spark to the other side.

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Thanks. First, replaced both plugs. Yes, it starts with right side plug disconnected, but not visa versa. I then tried new coil on right side but this side is still not sparking. Thinking it is the ignition module, but is this designed so that one side only could not properly getting spark? It's an expensive part to trial and error diagnose...