I started my car a few weeks ago, and the check engine light came on and the S light on my dash kept blinking. Followed by a difficulty stepping on the gas pedal. I attempted the paperclip way of scanning my OBD1 scanner. When I used it, the check engine light went off, no S light blinking anymore, and the gas pedal worked great! I also changed out my VSS (vehicle speed sensor) but the light came on anyway, and my speedometer can’t read at correct speeds. Could the engine light problem be because of misfiring due to spark plugs? I’m ripping my hair out trying to figure this out!! I don’t want to keep buying parts and stuff unless I’m 100% sure it will fix the issue. Any ideas or suggestions would be greatly appreciated 
Here’s the diagnostic procedures for a blinking ‘S’ light for your 91 Accord.
http://techauto.awardspace.com/transmission.html
From what you describe, the problem might be with the Transmission Control Unit.
The TCU is what takes the signal from the VSS and applies it to the speedometer. And since you’ve replaced VSS and it didn’t fix the problem, I’d take a look inside the TCU.
Tester
The resistors and caps go out in the tcu. They are fairly easily replaced if you or someone you know can solder?
I’m wondering why you replaced the VSS? Was this b/c the S light was blinking? You mentioned that all the problems went away after you checked for OBD I codes. Have all the same problems returned after you changed the VSS? Have you tried installing the original VSS? BTW, did you find any diagnostic codes stored?
One thing, this is going to be tough for you to fix if you need to be 100% certain of the diagnosis before you buy any replacement parts.
I replaced the VSS because my speeds weren’t reading accurately. The engine light and S light aren’t on anymore, but my speeds still won’t read correctly
And the gas pedal seems to work now, not difficult to press? Does this car have cruise control?
The car has cruise control but I’ve never used it. And the gas pedal is smooth as ever
If you used the paperclip method to read the codes…how about letting us all in on the secret. What codes came up???
Yosemite
There were no codes! That’s the strange part
The last Accord of this vintage that had this issue…quickly progressed to not being able to shift thru the gears when the shifter was in the “D” position. It would however shift when you moved the shifter thru the gears…
I replaced the Transmission ECU and the issue was Instantly resolved. After the Trans ECU swap you could put the car into “D” and she would shift thru the gears as it always did when the car was younger.
You might be heading toward this same Problem/Solution? It actually cost me 10 bucks to repair… Car is still running and shifting just fine today…this was 3 yrs ago. This vehicle should have a separate Engine ECU and also a Trans ECU… I repaired this problem using an ecu from a U Pull it salvage yard…so the cost was MINIMAL to say the least. I found out later that this is a fairly common problem, not sure if yours will progress to this point but… the info here is valid. Let us know what it was…
Blackbird
Good ideas above. Another idea, if this happens again, see if you have accidentally turned on the cruise control. If there’s a VSS fault, that will annoy the cruise control, and it is hard to say how it might issue its complaint.