I do not know what I'm missing here, but the problem is very consistent...I've tried almost everything else but witchcraft...

Condition:

At start lambda 0.8-0.9.
When warm-up enrichment cease lambda rises to 1.0.
After few minutes of idle lambda 1.1.
Increasing revs idle-4000 rpm, car stationary, lambda rises to 1.2-1.3
Over 4000 rpm ( exact switching point unclear ) lambda drops to 1.0!

Now, when all leaks have removed from the equation, this happens whatever the combination of parts is, ie.
-no matter if it's blow-through or std location MAF ( Hitachi used )
-no matter which set of WBO2's I use ( have two ), NBO2 voltage seems to follow WBO2 indications
-TB used now is 996 turbo std
-Forge DV's are used as BOV's but they're before the MAF and don't leak.
-exhaust has 100 cell HJS cats, new flanges and seals
-there's no fault codes
-connection from oil tank vent to intermediate piece ( that T-piece ) is blocked, all vacuum connections are checked
-997 GT2 aluminium intake distributors, gaskets checked, rubber sleeves connecting them to intermediate piece OK, intake side pressure tested
-aux air passages at heads blocked
-switching off cam lift or valve timing via Durametric affect engine's idle, so I assume that all solenoids are operational

Could it be possible that fuel tank vent line valve or it's check valve is damaged? I'll disconnect it during the weekend for trial anyway...
Where the possible leak -if any- could lay? Forge DV's are used as BOV's but they're before the MAF and don't leak.
How about N75 valve:



Atmospheric Pressure is now connected to, well, athmosphere while the F-pipe hassle is deleted. IMO it can't flow "backwards", from Y-pipe to atmo, or can it? ( Actually I've once disconnected the whole valve without success. )
How about some sensor problem, like either IAT or MAP? Once again, no fault codes...

Any help appreciated!

 

is the car tuned? by whom?
sounds like a bad 02 sensor...


did you do a boost leak test from the TURBOS...

 

EVOMS
Two pairs used, other one is 1 year old , the other one 2 months, used for less than 12 hours. How about wiring...what to test?


Nope, not yet. Just from Y-piece.

 

if the car is running a blow-thru MAF, even with a leak after the turbos (but before the MAF), it won't affect lambda in any way, as air flow is only read just before the throttle body. Only leaks after the MAF can affect fuelling.

 

I've thought so too...

One more weird thing is that it did run properly during the winter's cold days, with OEM TB, Y-pipe and that Hitachi MAF at std location.

 

Was the diameter of the housing for the Hitachi MAF the same as it is now as a blow-thru? If it's different and you didn't get a retune for blow-thru, it makes sense that you're experiencing issues.

 

I have been running blow thru on my car for 6 years... I install them too... number 1 test I do whenever ssomething is off as a starting point is a leak test from the turbos... its like blood work...

 

I agree 200% with you for troubleshooting missing boost. However, in this case, a boost leak is irrelevant, as, if it happens before the MAF sensor it won't make any difference to fuelling, which is what pete is trying to troubleshoot here

 

I agree but I would still do it...
and yes the 02 sensor cables do get pinched often and as a matter of fact I seen that same problem due that... but do both sides cause the same afr issue or just one?

 

Can you see what afr's is your ECU requesting?

I would check things like O2 sensors, fuel pressure, and the MAF. My bet is the lambda sensors.

 

Both side WBO2's show similar values.

MAF housing diameter is similar within ( a fraction ) of 1mm, as a matter of fact if I move the MAF to OEM location the housing is exactly same what it were before this weirdness started.
Also sensor depth in the housing is the same. Program is ( supposed to be ) written for this combination.

Fuel pressure is normal ( = checked ).

Boosted lambda values are where they should be.

I think I'll measure wiring loom from between sensor connectors and the DME, just to be sure.

 

High-resistance short circuit to B+. Will renew wiring to both sides.

 

So, while there were no mechanical causes to this I started to look for electric ones. What makes fault finding difficult is that I have reprogrammed Motronic and I really do not know which fault codes have been blocked. I asked just NBO2's to be blocked, but so far I haven't got info if all oxygen sensor related were...
So I started with OBD Manual's code P0130...:

Work instruction:
1. Check reference voltage on component. OK
2. Check reference voltage on control module. Unable without that test adapter

4. Check wiring for short circuit to ground. OK
5. Check wiring for open circuit. OK

But 3. Check wiring for short circuit to B+. Measured following voltages:
Pin II/9 and gnd 2,5V
Pin II/15 and gnd 2,96V
Pin II/2 and gnd 0,35V
Pin II/5 and gnd 0,35V

Right bank shows similar values. According to work instruction all of these should be 0V. ( Although I did measurement with cold engine... ) Corrective action is to repair wiring & correct the cause of damage.
Now the million dollar question:" Where that short to B+ may be?", if it's not in the WBO2 wiring, which I have just replaced without any help. Or is my Motronic toast? If yes, why?

EDIT: Did some more fault seaching.
According to fault code P0103 MAF B+ check OK.
According to fault code P0112 & P0237 ( or 0238 ) IAT & MAP B+ check not OK, found +5V.

Disconnecting connectors ( breaking points ) X59 1/2/3 ( = separating the engine ) does not help, ie. the fault is not at engine wiring loom.
Disconnecting Motronic connectors C/D/E and leaving only A & B, power feed and WBO2,, does not help.
Removing fuse C1, engine electronics does help...

Is there a way to get the Motronic tested for internal faults? And also repaired?