After driving for a while, why does the engine light come on?

Question

I get a code P0305 and at the same time the electronic speedometer becomes erratic. Everything was fine until I bought fuel that was ethanol free. The "misfire" became pronounced. I have run fuel sense then, with HEET, after replacing the wires, plugs, cap and rotor. I used Motorcraft plugs. We found the fuel filter had been installed backward and replaced it. I replaced the air filter, and decided to replace the battery. I have been using 87 octane, which is what the van calls for. It does have 246,000 miles on it, but burns oil like a new car. Haven't done a compression check. It doesn't sound like any lifters have gone bad and I run 20-40W oil. A mechanic said he "thinks" it's an injector, but advised that I should continue to flush it, with additives when I fuel up. The freeze frame said the code occurred at 2600 rpm, but everything else appears normal.

Answer 1

P0300 Random misfire

P0305 Misfire number 5 cylinder

Fuel injector cleaning is a good idea, when it comes to fuel distributor they have no control over the fuel they distribute, it is all dependent on the local market, Use the recommended octane and nothing higher.