Shinhoto

I usually let my 94 pick-up warm up for about 5 minutes each morning. However if I don't, the check engine light comes on. I can pull over, restart the truck, and the light goes away and stays away.
It idles a little rough sometimes, but more of a gentle grumble, not enough to male me suspect a misfire.

This weekend however, I decided to run it on 90 octane gas to see how my mpg and engine would react. I didn't notice a bump in either, but while out on my trip, I made the mistake of downshifting from 5th to 4th.

That really did it I guess, the check engine light came on, and will come on again randomly even when restarted. Nothing else has seemingly changed, except the fact that the light is on.

I got my codes this morning, 14 (ignition reference signal - no signal), and 52 (knock sensor KS - circuit). Code 14 seems like it can be a little elusive to track down and rectify, possibly coming from a wiring, ignition module, or ECM issue.
Code 52 should be having pretty noticable impacts on my truck, as it is supposed to retard the timing and place the truck into limp home mode. On my drive back, I drove at 70 mph no problem, seemingly no loss of power, and no rough(er) running.

My plan right now is to finish off this tank of 90, refill with 87 and Lucas FOT, and clear my codes and hope they stay cleared.

Plan B is to finally change my valve cover gasket, put in some new spark plugs, and clear again.

Plan C is to weep.

ev13wt

downshifting has nothing to do with the light. Start with the ignition reference signal.
Octane rating is irrelevant.

I can go 70 in "limp" mode in my 22-re with 4.11 difs and 31" tires. It will do 90 at 4000RPM when not in limp mode, 85 with throttle barely pressed.

Shinhoto

I'm going to see if I can test the distributor myself, and then replace it if necessary.

While doing the valve covers I'll also have a look at the knock sensors, and possibly replace them.