Need advice on trouble codes

[Firescooby]

2003 Toyota Corolla CE 5 speed
131k miles
Bought at 125k miles 4 months ago

History:
About a month ago I used Seafoam through the brake booster vacuum line. Immediately after, the check engine light came on. I reset by taking the battery cable loose. All was fine, no light, still running a little rough when really cold in the am, but better.

Four days ago, light came back on. No noticable change in running. Took to autozone and the codes were:
P0300 (Random cylinder misfire)
P0301 (Cylinder 1 misfire detected)
P0303 (Cylinder 3 misfire detected)

I don't know much about the maintenance history, not sure if plugs and wires are in order, or if this is something related to the Seafoam (my suspision), but what.

[mikered30]

It is likely the seafoam dislodged carbon. Since you do not know the history, it would be a good idea to change or at least inspect the plugs. Stick with iridium plugs, NGK and Denso work best and cost around $32 for a set of 4.

[tarbasd]

+1 for replacing the plugs.

[dorman68]

Originally Posted by mikered30

It is likely the seafoam dislodged carbon. Since you do not know the history, it would be a good idea to change or at least inspect the plugs. Stick with iridium plugs, NGK and Denso work best and cost around $32 for a set of 4.

Definately the plugs. Also if that does not cure your problem I would check the intake manifold gasket for vacuum leaks, I have heard that this is a common issue on the 9th gen rollas with the 1zzfe engine.