henrybayuzick

Hello,

Always fun buying a car from an older lady who doesn't know much about the car.

Anyways, a quick trip to auto zone and I'm left with these codes. I'd like to do all the fixes myself, and because I'm new to mercedes (coming from VW), would love to know where to the best place to order parts is.

The car:

2001 C320, Automatic, 105,000.

The codes:

P0300, P0304, P0306 (All misfire, correct?)

P0115 (Coolant Temp Sensor possibly?)

P0443 (Purge Valve clean? I have a guide written by ohlord on how to clean them. I don't hear ticking though.)

Appreciate any help. Looking forward to fixing these and the forum seems great so far.

mleskovar

Before you start fixing anything clear the codes and see which ones (if any) return.

henrybayuzick

Unfortunately I did and they all came back. :/ Let the fixing begin!

Glyn M Ruck

I would clean all connectors first & look for corrosion. CRC switch cleaner or similar would be perfect for temp sensor & purge valve. Otherwise toss the purge valve. They never clean up properly. EECS (evapourative emissions control system) codes can drive you mad with little really wrong.

300 codes for misfire then donated by cylinder number e.g. 306 = cyl 6 are easily sorted by moving wires or coils & seeing if the code changes cylinder.

It is likely coil packs or leads. At the age of your vehicle I would change all plug leads then see if you have a coil pack problem.

On twinspark engines plugs are seldom the problem if serviced to the book but if you have never changed them change all 12.

Check fuel pressure at the Schrader valve on the fuel rail connecting the injectors. s/b 3.8 bar or 55 psi while cranking.

Good luck!

mleskovar

The 300 (random misfire) is probably related to the 306 (misfire cylinder 6). After plug inspection you can move wires and coils between cylinders to narrow down the culprit. 0400 = EGR flow problem could be the tube going into the manifold blocked with carbon/gunk and 0443 = Evap emission control.... I believe (?) over filling the tank can take out the purge valve but first check that the gas cap seal is OK. There's been several posts on how people tracked down these two problems. Does the display show engine temperature properly and is it around 95C?

henrybayuzick

I cleaned the purge valve yesterday following an older ohlord guide, I'll clear the codes and see if it comes back, it felt too simple to work. If not, you suggest just buying a new one? What are your preferred sources to buy parts for your car?

Regarding changing the leads (are they the same thing as plugs?), are there any guides floating around showing how to replace the plugs and also the coil pack? I haven't quite found my way around the engine yet. What spark plugs should I use?

"Check fuel pressure at the Schrader valve on the fuel rail connecting the injectors. s/b 3.8 bar or 55 psi while cranking." Care to explain more? I have absolutely no idea how to do any of that.

Appreciate the reply.

henrybayuzick

Can anyone confirm that the P0115 code is temp sensor? And if so, where a good place to buy it would be. My local dealer wants $28 something. I've heard it's cheaper.

Thanks.

Glyn M Ruck

PO115 is definitely the temperature circuit of which the sensor is part.

Ohlord is an extremely competent individual & has regrettably left the board due to bad behaviour on other forums. My experience with purge valves is that they are better replaced but they usually get noisy ~ loud ticking.

Plug & lead replacement is covered in the Wiki & the DIY stickies.

Leads are what connect from the coilpacks in the cam covers to each plug.

I use RMeuropean for online spares.

You should use OE NGK or Bosch plugs of the original value. RMeuropean can provide them too.

Fuel pressure is checked with a pressure gauge that you can usually borrow from your local parts provider at the bicycle type valve on the fuel rail. See fuel rail pic. Pull off the aircleaner housing & all will be plain.