06 prius 220k miles, been running great, until have a upper motor knocking noise,,but rev it up and it goes away,,, now the red triangle light is on,, havent checked the meaning of it,, thinking of replacing the injectors, number 3plug looks black,, really at wits end with diagnosing ?
A fouled plug can indicate incomplete combustion. Did you check the ignition? A good mechanic can suggest some things to test, but I wouldn't be tempted to start replacing things just to see if it helps. Much cheaper to read the codes first.
I think you're correct - I remember looking at a replacement Corolla for my previous Toyota (before I purchased The ChuggyPig) and my tame mechanic informed me when he scanned the reason for the CheckEngine light being on, 0420 came up, and his advice was new cat/conv ($800 just for parts) - his advice was "Tell him thanks, but No Thanks!" - (My two furry CellMates just looked at me with puzzled looks, wondering why I should want to get a new cat when there are two perfectly functioning feline specimens already in the house (…and they've each been fixed!) - Wil
That sounds more like wild guessing than "diagnosing". If one plug looks bad, replace the plugs first; they are relatively inexpensive. Next you need to hook up a code reader and see if any trouble codes are set.
