2000 RPM, trailing throttle.

[HRG]

What occurs specifically at 2000/2200 RPM on a trailing throttle? I have an intermittent shunt that is reproducible by sitting at a fraction over 2000 RPM and then feathering the throttle. I don't think it happens on a fully closed throttle, although it may just be that the car falls out of the affected rev range in that scenario.

Without knowing what sensors are firing or what is changing on the map I'm 100% certain an event triggers at that precise RPM that the engine isn't happy with.

I can drive through the shunt quite easily if the throttle is open.

What should I be testing and what's the procedure for testing said items?

[GreenV8S]

Could be you are just on the verge of overrun fuel cut-off? This causes a sharp increase in the amount of engine braking.

[HRG]

Doesn't that usually cut in at slightly lower RPM? From memory she seems to drop to about 1200 RPM, hold for a moment then return to idle.

At what RPM does the stepper motor fall out of the equation?

[HRG]

Is it possible to download any software to run on a lappy and see what the standard ECU is saying?

ETA:

What turns off the cold start enrichment? 1/4 tank for 38 miles of normal driving makes me think the problem is over fuelling

Edited by HRG on Monday 14th July 08:40