I have been experiencing an intermittent problem with the engine cutting out. Driving at various speeds the engine stumbles at random times, coasts for a bit and then I get my throttle back. I realized the last time it happened that my hand was lightly pressing on the right horn button while I was holding the wheel. I pressed the button a bit harder, short of making the horn sound and the problem got much worse but as soon as I let up, car ran fine. 30 minutes later car did it again for longer period but I was not touching the horn button. I pulled over since engine was just idling, put it in park, then pushed the horn button several times. After shifting back to Drive, car ran fine for the next hour and still does now.

I took the horn button off and looked for evidence of frayed wires and a short the next day. Not only did the horn work fine, (it rarely does using the right button), but all wires and connections looked fine. I disconnected one of the wires and put things back together. The left side horn button works fine so I can still sound a warning if necessary.

Is there anything else you can think to check that I haven't.

Fuel pumps have been replaced along with the O2 sensor which was the original (306,000 miles) and various relays have been checked along the way to identify the source of the problem, to no avail.