[V8] Idle Stabilisation Valve

[CavalloGT]

Tom,
With regard to what you are seeing with the idle speed being high in spite of having swapped the ECU from your other vehicle that does not exhibit the concern:
One of the ECU strategies that controls/effects idle is what the ECU perceives as the current charging system output. If the ECU senses low/erratic charging voltage, it will raise idle speed in an attempt to increase alternator output in an attempt to help keep the battery charged. This is a foundational strategy, and while I cannot say with 100% certainty that Bosch has employed it in this system, I'd be surprised it it didnt. The fact that you swapped ECUs and the idle valve still remains in a high idle position suggests that there may be a charging system/wiring issue, which the ECU interprets as low charging voltage. This of course assumes that the idle valve and it's associated wiring are in good working order. Simple testing of ECU power and ground circuits can be done to check this, as well as proper charging system checks. Remember open circuit voltage testing is useless, as the only true measure of circuit performance is dynamic load testing, and pulling a pattern of charging output to be sure excessive rectifier noise is not an issue.
Good LuckGT


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