I was changing my oil/filter, transmission fluid and air filter yesterday with a buddy of mine, the job goes well and I'm on my way, but about an hour and and 30 miles later my check engine light comes on accompanied by inconsistent revs (normally idles at about 650-700 but at the time was dropping to about 500 before the needle would fall to 0 and of course the engine would die. Long story short my friend neglected to plug a connector back to the air filter, allowing unfiltered air into my engine. My question for you guys is what, if any, is the extent of the damage that could be caused by this, did I mention I drove through a nice cloud of dust and debris kicked up by one of those, totally not a waste of tax dollars, oh-so necessary street sweepers, but other then that driving conditions were ideal. I know this question is stupid but I would really appreciate a more knowledgeable opinion on the subject. *Also I'd like to add the car is running normally after the hose was reconnected and the battery reset, I haven't noticed anything unusual thus far. *2004 Honda Accord EX 4 cylinder.

 

Since it didn't seem to cause any immediate emergency, you're looking at long-term subtle damage. Like for example a little bit of extra abrasion on the cylinder walls. If you're really worried you can have the engines compression measured. But you won't have a 'before' number to compare against?

If I were you I'd change the oil & filter now just to remove anything that might have got in. If you're into oil analysis, THIS oil that drains out will probably show elevated silica so it may be useless to get an analysis. If you want, get it analyzed next time.

 

I got your note & picture, but that doesn't really change anything. That thing is part of the crankcase vent system, & probably why it set off the CEL. Unless you really had your foot in it when you went thru that dust, it probably got very little in there anyway.

I really don't think you should do anything beyond changing the oil & filter. Then maybe measure compression.