I recently changed the spark plugs and wires on my 2002 Ford Focus SE with Zetec (DOHC) engine. I used NGK TR5IX (7397-4PK) Iridium IX plugs and Motorcraft wires.
When I received the plugs, they were gapped to about 0.03'. The owners manual it says gap should be 1.3mm (0.051 in) and most online sources I found agreed, so I set the gap to 0.051
But now there is a rough idle, and when I first start going it is really sluggish accelerating (it seems to get better once I've been going for a minute or so). But when I stop the car and let it idle, the engine has been dying (it starts right back up no problem, though, and doesn't die while moving).
I am not sure what could be causing the problem. Is it possible that the plugs I got need to be gapped differently from the manufacturers recommendations? Also, there was some rust around the spark plug wells that I tried my best to clean off before removing the old plugs, but a (very) tiny bit of rust dust fell in when I pulled them out. Could that be it?
Anyways, I don't know what to do at this point - any ideas how to diagnose what is wrong? Thanks!
UPDATE: Ugh ... right after writing this, I discovered the problem: Amazon's crappy car part compatibility tool suggested the wrong plugs for me (2nd time: they also sent me the wrong PCV valve ... definitely won't trust it anymore). So I have requested a refund, and will get the new plugs tomorrow from O'Reilly ... but in the meantime, I guess that changes my question to whether or not I could have caused any permanent damage driving around for about an hour today with the wrong plugs?