I have a 1995 C280. It only has 126,290 miles on it. I scanned my car and this is what I got:

P0400 exhaust gas recirculation flow
P1170 short term fuel trim malfunction
P1700 up-shift delay switchover valve without function (logic chain)


What is the up-shift delay switchover? Everyone on the posts keeps saying to go buy a new one, but then I search online stores and can’t find anything close to the up-shift delay switchover valve?

Does anyone know another name for the part so I can replace it, and does anyone have a diagram of a 1995 C280 that might help me find my way around under the hood?

Also when I am parked with the car running, if I have my interior air on my car makes a loud kind of clicking sound, or stuttering or putting sound coming from the fan and fan belt area. If I turn off my interior air it gets a little quieter but it still makes a noise. (the noise kind of sounds like a muffled version of a card on a bicycle wheel hitting the spokes, not as clunky but more muffled or something)

Does anyone know how to change the serpentine belt, and how I can change my cars tension pulley? Cause I am assuming that is the reason.

 

My guess is that you might have a blockage in the EGR tube. By now you've probably already found the fix. What was it?

Unless your serpentine belt is worn I wouldn't change it. The serpentine belt tensioner might fail. The little rubber hubs do wear out and then you get to replace that too. Have a look at the pictures of new tensioners on the autoparts sites and you'll get an idea of how the tensioner works. Very German! I changed my tensioner on my 94 c280 and it was quite the hassle. Have you changed yours yet?