I power washed my 1996 mercedes benz c280 and now it idles funny and the check engine light is on why? It ran perfect before power washing the engine

Your silicone wires are leaky- replace. Cap may be cracked, look for carbon traces inside. A generous cloud of WD-40 (water displacer) is an OK temporary solution. (Jayster- Guy who used to pressure wash the engines frequently in Berkeley)

Awesome answer sir.

96---how's it holdin' up? upholstery still free of rips? Smokes? over 300K?

In the words of click and clack wash the windows, NOT the engine!

my suggestion is to get an obd II reader and see what code you're coming up with before you replace anything. you can diagnose this for about $30 if you have a smart phone. ELM 327 obd II bluetooth code reader and the app called Torque.

Perfect condition I got it from the original owner no rips or tears in the interior and ran perfect until the power washing thanks for your answers gonna check it out today

I agree it could be the wires but it could also be water in the air filter box ive had that problem before both with my own vehicles and vehicles i detailed for customers when i started out as a detailer if water has gotten to the the air filter just remove the filter dry out the box and let the filter dry out before placing it back in hope this helps