Am unable to clear a CEL Code P0170 (lean fuel trim left bank).

Car is a 98 C230 /auto/95000

So far I have :
replaced spark plugs
replaced fuel filter
replaced air filter
replaced MAF
replaced O2 sensor (front)
replaced EGR

unable to find any vacuum leaks and use premium fuel

Have cleared the code a number of times and car starts/runs fine until CEL comes back on (2-3 days) . When CEL is back on the machine stumbles at low rpms when first started in the am......then seems normal after a couple of minutes.

My feeling is that it is some kind of EGR/Vacuum leak as the problem seems to be a cold start (open loop) issue. It seems like once it goes to closed loop in runs OK.

Any help/suggestions would be GREATLY appreciated as DIY info on any MB site is most difficult to obtain. My last resort will be a M ega B uck dealer.

THANKS!

 

My best suggestion, take it to MB and Pay them for diagnosis only!! Maybe cost upto 1 hours labour.

Then when they give you the virdict, and estimated cost - tell them you getting rid of it so you dont want the work doing by them.

You're clearly very capable (mechanically) as you changed loads of parts so far, but sometimes - like all of us, you have to ask for (tiny bit) help, and tif thats the dreaded Stealership...$$$££££$$$£££

Best of luck andkeep us posted.

My one only suggestion mabe a BadCAT or O2 sensor, mine has a total of FOUR!!

Cheers
Peter 2001 C320 (W203)

 

Peter....Thanks for the prompt input.......the stealership is a final option and had planned on doing as you suggested......I can domany of the things myself....BUT... this one has me grasping.........

Thanks again......

 

Have you thought of calling them and just ask for some general advice.

Certainly here in the UK they can be helpful.

If not, I'll go and see a MB tech chap at my dealer, I get lots of info including the odd freebit during the service, as I get on with him quite well.

Let me know
Peter

 

I'd certainly be fortunate ...IF I knew a skilled MB mechanic....sadly I do not.

As to calling them for advise.......here in the "colonies"..... I would expect them to tell me to ..."make an appointment"

I'm not sure how much info a dealer can provide.....my code scanner gives me the fault code but does not give a specific component malfunction. Most mechanics tell me they just start the search from that and begin eliminating the potential causes (which is what I'm doing). The good news is that I do it a LOT cheaper than the dealer.

With that said....I may still have to take the puppy in and see what they say/recommend.

Thanks again..........

 

Does your code reader connect to a laptop or standalone?

I bought a SERIAL connected cable that connects to my laptop, www.ukobd.co.uk £64.95
With free delivery.

It comes with DIGIMOTO Lite free, which does not show the fault code description, just the code.

HERE'S the good news, I fould free software from germany that actually gives a description. [8D]

Keep me posted if you do find anything else, I will do the same

Peter

 

My code scanner is a stand alone/hand held. It gives me the code number ie: P0170 (lean fuel trim/left bank).

As I mentioned before I don't know what the MB dealer gets on their scanners....BUT I suspect they only get the code and NOT any specific cause. Their guess is probably a little more definitive than mine ...BUT considering the $$$ involved I opted to do my own parts swapping.

The arguement can be made that THEY would have fixed the problem....................

The hunt continues......did another reset yesterday after 3 days of no light.

 

OK...latest is I talked to a local mechanic and ran him through the whole senario .

His suggestion is to check the plugs for fouling which should lead me to a INJECTOR issue . He suggests that if that is the issue...replace the bad injector.

I can't understand how that would only be an issue in "open loop" but am willing to look at all possibilities......will tear into it next week......have a golf tourny the next couple of days.

 

bumpity

 

Codes p0170 and p0173 are called self-adaptation at load limit values. Is this a naturally aspirated or supercharged motor? The air mass sensor will remedy the problem 98% of the time. Where did you get it? I would check for vacuum leaks and then check the wiring harness to the air mass. Use a razor and gently cut the insullation parallel to the wires and inspect for deteriorating insulation between the 4 or 5 wires to the sensor Which will cause cross shorting. If you can't erase the code immidiately, you are looking at a problem with the generic code scanner that you are using. Euro cars had many issues with obd2 compatibility. I have seen rare occurances where the throttle actuator will cause this code but there are other symptoms like intermittant stalling, high idle, fluctuation in idle. I would check the wiring harness and only install an OEM air mass sensor because over 50% of the aftermarkets are junk. I have never seen a mercedes electronic fuel injector fail and doubt it would be that code so I doubt that is it either.