05' C230K sedan (W203 M271)
 

Over the past couple months we have been getting random misfires error P0302, changed plugs twice now and things got better. Ran it with a bunch of cleaner and have only used higher spec brand fuel. Well those errors have pretty much gone away. I attributed it to my GF driving the car like a grandma(not the fast ones either).

Well now we have a whole new set of problems that just popped up. The car acts like it will not build boost under throttle, it idles fine and even runs ok under very minor throttle, but forget anything close to full throttle. A bunch of new error codes came up and after clearing them, they immediately come back.

P0031 - HO2S Heater Control Circuit Low (Bank 1 Sensor 1)
P0037 - HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
P0075 - Intake Valve Control Solenoid Circuit (Bank 1)
P0414 - Secondary Air Injection System Switching Valve A Circuit
Shorted
P0448 - Evaporative Emission Control System Vent Control
Circuit Shorted

Any ideas or maybe someone has been thru this before?

Here is some background on the car in case anyone sees the significance, 102K miles on the little sport sedan and pretty much has led a very charmed life, no issues whatsoever before this point. I replaced the valve cover gasket about a month ago because I saw a bit of oil weeping around the spark plug holes.

We contacted a couple of the local dealerships to see if maybe we missed one of the TSB's or if it could be the leaking cam sensor issue but the fix was already done on this car. To me it seems a bit ridiculous that each of those O2 sensors could have died at the same exact moment along with the intake solenoid circuit, Secondary Air Injection System Switching Valve, and Evaporative Emission Control System Vent Control
Circuit all at once.

Thanks in advance

I've had an S class in that needed a new solenoid.

I can absolutely understand a single part failing. Just seems a bit far outstretched that all those components have decided to give up the ghost all at once.

Have you checked compression?

Has the wiring harness been inspected for oil intrusion?

I'll check both this weekend, and report. Anything else I can look for? The GF is already on me to sell the car as soon as I get it fixed. I think these issues out of seemingly nowhere have ruined her opinion of the car.

Update - Wiring looms over the top of the valve cover are pristine, no leaks from the cam sensors into the wiring. Ran a compression test and here was the results:
cylinder 1 - 152, 2 - 149, 3 - 150, 4 - 150

I guess I'm off to an indy to have a diag. done.

I don't know if those compression numbers are good or bad, but if good, you're lucky. The factory updated the fuel injectors which are supposed to correct the problem and eliminate carbon build up that ultimately wears things out. These engines develop misfires frequently and the fix is a very expensive valve job. We sold our C class for this very reason....

Yep, next available appt. at my most trusted independent shop is next Monday so I guess I will have to wait.

This little C Class is going away after this hopefully she goes quietly...:) and with minimal damage to my pocketbook.

Here's an update

Indy confirmed that there is major corruption in the wiring harness as he is getting very inconsistent readings. Recommends to replace the harness and start from there. Next appt. is in November as he is booked up (apparently very good and has an amazing reputation)