Lambda and mixture ECU errors on Corrado VR6

[ismith 0]

Finally got some ECU errors come through with my long-standing poor mpg. Any ideas?

 

The plugs are a little black, not normal. I've tried an ECU reset and training procedure.

 

The blue sensor was replaced a couple of years ago. With logging on VAG COM, it warms up beautifully in a sensible ramp from cold to 85C. The lamda readings start changing at 60.

 

The lambda was faulty once before and replaced and appears fine now - 0.95-1.05 on VAG COM when idling. The weird thing is the range of ADAPTATION values for idle, mid and full throttle (group 6). This previously was 0.9xx-1.0xx, but now anything from 0.400 to 0.999. (Today 0.415 0.992 0.922) I also checked the wiring from ECU to lambda and MAF and the supply to the lambda heater is good.

 

The injectors have been overhauled and I've tried a new MAF. The fuel pressure is spot on (3.5 bar idling, 4.0 bar on throttle blip.) Compressions cold and hot are well within spec, although there is some oil consumption (around 0.5 l /100 miles). I also checked the evap purge valve closes after start.

 

Is my ECU failing?

 

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VAG-COM Version: Release 311.2-N

 

Control Module Part Number: 021 906 258 B

Component and/or Version: MOTOR PMC 1

Software Coding: 0261200494

Work Shop Code: 1267357207

2 Faults Found:

00537 - Lambda (Oxygen Sensor) Regulation

11-10 - Control Limit Not Reached - Intermittent

00561 - Mixture Adaptation

15-00 - Adaptation Limit (Add) Not Reached

[dr_mat 0]

Black plugs deff indicates overfuelling (matching your poor mpg). I would suggest you start looking for hairline air leaks in the exhaust manifold, pre-lambda.