E38 - Commodore OS 12635863 - Low INJ PW on Initial Start

[Jasper]

Currently I have the airflow meter parameters set to force a failure and operate in SD mode while I try to tune the fuel and timing maps.

Every time I start the vehicle after it has not been recently running, the ECM commands smaller than normal injector PW, and the engine runs lean as the Dickens, usually stalling if no accelerator pedal input is used.

When turned off and restarted the INJ PW are normal, and it idles perfectly, very close to the commanded AFR.

Attached is a log of the first start and restart, the following screenshots compare the two situations by filtering the data for runtime >0 and either ECT>34 or ECT <34.

INJPWB1 on first start:


INJPWB1 on restart (note much longer PW at idle cells 35 and 40kPa, 800rpm):


The cause is not the commanded AFR - as these are the same for both cases:

Commanded AFR First Start:


Commanded AFR Restart:


Does not appear to be due to an error in calculated air per cylinder either, as the logged APC is slightly higher in the cells of interest during the first start.

APC First Start:


APC Restart:


It appears that the ECM may be using a modified injector flow rate based on the engine offtime when starting. I am not aware of anything (visible) in the calibration that would cause this.

Any advice?

[Jasper]

Following up a suspicion that I had not "failed" the MAF correctly, I unplugged it, which caused the lean running to persist after restarting.

Now after altering P0101, P0102 and P0103 to A: 1 Trip, Emissions Related; and leaving the MAF unplugged, I am having more success with tuning the VVE table.

[joecar]

+1 I agree, a MAF DTC indicates SD.