Rep Power: 0

I just bought an 04 civic. I used degreaser all over the engine and then pressure washed the whole engine. Letit sit for about 30 minutes then drove it home. Driving home it was shaking and the check engine light would come on and offf. The intake was off when i washed it. I dont know anything about cars so not here to get judgement... I opened the hood and will leave the car to air dry for the next 2 days without driving it. The car starts up but it shakes now and sometimes gives the check engine light on and off. Any thoughts?

 
Rep Power: 517

Would help to know what the code is. Should be a misfire code if it was flashing the light at you. Not really needed though.

Remove the ignition coils (lay them out in order, keep them in order) and see if there is water on the tubes and in the spark plug wells.


Use an air gun to blow the water out.
Or...Possibly a shop vac -- with a straw and duct tape.

THEN I'd remove the sparkplugs and look for arc trails (carbon tracks) down the outside of the porcelain.





If you find any, that's bad. That means the corresponding coil boot is also probably damaged from arcing (didn't see my usual pic of that right away though).
Replace any that show arc damage. I'd replace the corresponding coil(s) too.

Dry everything thoroughly, plugs and coils.
Reinstall and pray to the deity of your choosing that it runs right.

You mean the air filter housing lid? That's bad too. Engines do not like water.
Open the throttle wide open and look down it with a flashlight. Is there water standing in the bottom of the intake manifold? Try to suck that out too, if you find some.


HTH