Hi all

I have recently replaced a lot of parts on the C230.

2005 C230K Coupe
M271

Here is a list:

1 - All breather pipes, (even under the supercharger)
2 - Cam magnets and the harness.
3 - Maff ( Not Original)
4 - Upstream Oxygen sensor(Original)
5 - Downstream Oxygen sensor(Original)


My problems are as folow:

1-Even after replacing everything I still get a 171 code( System Too Lean Bank 1)

2-My upstream oxygen sensor has a voltage of 1.508v and sometimes changes to 1v or 0.980v

3-Short term fuel trim runs on 0% and sometimes runs into negative

4-Long term fuel trim stays at 25% and does not even move



Is my ECU stuffed? or is there something I am missing?

 

My bet is a vacuum leak.

double and triple check all hoses

 

No vacuum leaks, checked all.

 

Non-original MAF sensor is suspicious. I am not sure aftermarket ones work on these engines.

 

That is my second guess also. MAFs are not all equal.

 

That is true, but even when car is not running the reading stays at 1.5v. When I start even if the Maff is not doing the Job original does, should the volts not change on oxygen sensor?

If the ECU was faulty a lot of other problems would be visible? I can not imagine that just this one fault keeps coming up. Could I have a leak or fault on my injectors?

 

I don't think M271KE got MAF, it has "2" intake pressure sensors, isn't..?!?

ZAYED,,

 

Any leaks in the brake booster? I just replaced mine for this, and finally after doing what you did, passed CA smog.
It was hissing you could hear it....

 

Hi, I will have a look when I get home. Would the brake booster make me use more fuel? This fault finding takes a lot of time. I don't mind but its cold over here so hands suffer.