jsordelet

*My car is a 2009 C300 4Matic still under original factory warranty until July (then CPO kicks in)*

So, my cel came on the other day and I am wondering if anyone here can help me narrow down the root cause. About 3 weeks ago I changed the engine air filters but the car has driven fine since then with no cel. I went to an auto parts store and used their OBD2 to find the code and it was: "P0172 - System Too Rich (Bank 1)".

Could the changing of the filters have caused something to happen?

I am taking the car to the stealer on Friday for an oil change and have already asked them to look into the cel while its there. Hopefully, whatever it is, is covered by warranty.

Any thoughts?

xjaymzzx

What air filters did you use? K&n? Bmc? Those are notorious for giving cel lights

jsordelet

I used Wix filters

xjaymzzx

If the air filter contains oil, it'll sometimes drop lil bit onto the maf sensor (happens with over-oiling k&n filter. Oem air filters (paper) does not have it. I never heard of wix tho .

jsordelet

To add to the "wierdness", this morning when I started the car the rpm's were reving up and down. It was very strange. I put it in neutral and gave it some gas and then continued on my way and it did not do it again on my 10 mile drive to work that included a lot of idle stops at lights. I am wondering if it will do it again when I leave work tonight.

xjaymzzx

Try to put oem filters back on. And see if it goes away.

jsordelet

I would but I threw them away! I guess we will see what the dealer has to say on Friday.

xjaymzzx

Yeah I was thinking about changing my filters to performance filters but I don't want to risk hurting the engine. I say stick with oem.

Domm

Did you make sure that you installed everything correctly? Make sure all the filters are seated correctly and that all the parts you removed are put together appropriately or you'll get a CEL.

LILBENZ230

If it has a MAF problem (and it sounds like it might, or a vacuum problem) and you take it in with oiled filters in it the warranty is not going to help you.

Knightmare69

Wix filters are pretty much like mann filters, there shouldnt be any oil used.

slowc

Check Tps or iac

jsordelet

At the dealer now and it turns out the engine cover was not on perfectly, leaving a small gap near the MAF. Service guy secured the cover and now all is good. No cost to me!

steveneashcraft

I'm curious why an improperly installed engine cover would cause this symptom.
"At the dealer now and it turns out the engine cover was not on perfectly, leaving a small gap near the MAF. Service guy secured the cover and now all is good. No cost to me!"
Nice dealer. Most of them are!!!!
Any ideas? I can see why an improperly installed cover might allow air to get to the MAF without going through the air filters but I wouldn't expect that to make the car idle fast. If the mechanic found a loose hose that was allowing an air leak that might do it. Just seeing if anyone else has a thought on it.

Josh.A.Hussey

Agreed... Seems odd.