Hi CO on 3.0 CSI. Help please.

Hello Dr D-jet,

Meet the new member with an old problem.

I have fallen my recent MOT (ITV) here in Spain with my E9 because of 8% CO.
After searching around and checking and tuning everything I could bring it down to 4.5 % and that's it.

My check list was as follows:
1- air tem sensor (within tolerance)
2- coolant temp sensor (new one with a bit better tolerance than the old one)
3 - MPS sensor (absolutely ok according electrical and pressure tests.) I tried broken one and I couldn't notice dramatic changes in CO by the way.
4- injectors (a set of NOS I bought recently)
5- fuel pressure regulator (2 bar. Tried to low to 1.8 bar just for experiment  - no changes)
6- throttle sensor (0 Om closed, infinity after small pushing, 10 fluctuations 0-infinity after, so looks ok)
7- Ignition timing (checked and according to BLUE BOOK)
8- dwell angle (37)
9- spark plugs (new set of BOSCH W7DC)
10- valve clearance (checked and according to BLUE BOOK)
11- all wires and plugs between sensors and ECU (tested with multimeter and ok)
12- potentiometer on ECU (was in the middle when CO 8% was registered and in max anticlockwise now with CO 4.5%. So it seems like it works but maybe not as it should work. I'm not sure).
13- compression test (10.5-11.5)

After all these done should I still looking for some critical point I could missed? Or should I try another ECU (0 280 001 007) + MPS (0280 100 030)?
If yes please help me with a trusted source for these parts (you know prices and I have bad experience with a "NEW" MPS already).

Any help would be appreciated because I can't complete my car registration without this MOT (ITV) test.

Hope for your answer,

Regards,

Yury.







 

Hi Yury,

such a high CO normally comes from

1. MAP sensor
2. Engine temp sensor
3. Cold start valve
4. Vacuum leakage on manifold
5. ECU in rare cases, but then it tends to be higher CO

Hi Volker,
Thanks for your answer.

1. MAP SENSOR. I have 2, both tested for resistance and pressure.
2. ENGINE TEMP SENSOR. I have 2 the used one and the new one installed at the moment. Both tested for resistance. Both in tolerance. I tried to swap them and CO is changing about 1% depend on sensor installed.
3. COLD START VALVE. I made CO test with valve disconnected and hose plugged. No difference.
4. VACUUM LIKAGE ON MANIFOLD. I have 19 inHG at idle.

All wires from sensors to ECU are checked.
I tried to study your technical section before asking for help here first.
What exactly should I do first? It seems like I can't determine where exactly the problem is.

Could you help please?

Can anybody help?

Hi Yury,
19 inHg means about -0,35 Bar to us. I think, you should have a higher vacuum.
Do a search for vacuum leaks...

At first I would remove the hose towards the MPS, seal the support and try to apply a higher vacuum towards the MPS using a vacuum pump.
This is experimental - see what happens to the CO.

Regards
Norbert

Thanks you nordfisch,

It sounds interesting and I will try to play with it but I try to convert inHG to Bar and 19 inHG = 0,64 Bar according Google converter.

But nevertheless it't a good idea to confirm that MPS reacts on vacuum meaning.

Thanks a lot.