I got a Code P0171 this monday.
I try to replace spark plug first,maybe clean the MAF.
Car drive well but I feel idle more lower.
Does any advice to check or change first?
Thank you.

 

It would be helpful to know what engine you're talking about. It could be any number of things like weak fuel pump, bad MAF, bad injector, bad O2 sensor etc.

 

it's 2005 C230K

 

P0171 too lean. Means potential vaccum leak, ie bad hoses, ad or
as the man says, O2 sensors, MAF etc.

1st look for bad or leaking hoses, and clean the MAF see how that goes.
If you're not up to date on your maint. well it could be anything.

Read the codes with a Mercedes specific unit, you may get more info.

 

I got code 1 hour ago
P0300 P0301 P0304
Is it caused by vaccum leak?
or it's spark plug misfire cause P0171?

 

Oh...thats not good.
I'm not the M271 expert here. Hope others will chime in.
Early M271 had lots of problems supposedly fixed by new head design in 2005.
Still though, single row chain can stretch and cause all kinds of weird timing problems.

Have you kept up on standard maint? How many miles do you have?

 

I just bought this car three month ago.
142000 Mile.

 

P0300s is misfires likely because it's too lean still. Everything that's already been recommended still applies.

 

Fwiw, You're playing Russian Roulette with that POS timing chain.
If that timing chain breaks, then the whole engine worthless.

The M271 has one/few vacuum hoses that get holes/tears from heat and rubbing.
The good thing - the replacement hoses are cheap and easy to get.
The bad thing - it takes a few hours to get to and to replace the hoses.
A smoke leak test may be able to show a leak from that area/hose(s). Or, maybe not. It could be a small leak, and the smoke could get "lost/dispersed" before it can be seen.

Do a search on M271 hose vacuum leak.
https://www.google.com/search?q=m271+hose+vacuum+leak

Fwiw, I suggest replacing the M271 timing chain every 80K miles.
I have degrees, teaching, and industry experience in mechanical engineering and failure rates/reasons. So, my views may differ from other people.

Also, update your user profile to show car year, car model, and area in the world.

Good Luck!

 

Ah yes, the "$12 hose" . There's a thread on that around here.
Get it replaced for free at the dealer in the USA.

 

Can you give me more information?
Thanks a lot

 

Just google "$12 Hose C230". Lots of stuff...
my engine is different so no 1st hand knowledge.
Mercedes will replace the one hose for free, but any vacuum leaks will cause this.
And or O2 sensors, or MAF. I kept getting P0171 a couple years ago,
till finally read with actual SDS and it said straight up the MAF was shorted.

Of course this was AFTER I'd checked everything else, and I did end up replacing some split hoses,
and put in new O2 sensors since they were 'lazy' when I checked them in Torque graph and were like over 100K miles old and you're supposed to change them every 100K.

 

I had the same code pop up p0171 pnd mod1 and p0171 cnf mod1 1 both said bank1 system to lean. How ever the code came off a couple of days later. How serious is it if the check engine light turns off on own?

 

I drive a 2005 c230k im also new to this forum