Does resetting the red SES really improve performance?

[boustrophedon]

I have seen it suggested elsewhere that there may be a deliberate degradation of performance after the little green light go out and the amber and then the red engine service lights come on, and that resetting the service indicator tricks the engine management computer into giving you your power back.

There are suggestions that this is so that after an expensive main dealer service the car "feels so much better".

Hmm! Car manufacturers wouldn't cheat and lie with car software would they? Honestly if it were not for the recent VW emissions fiasco I would have dismissed the suggestion out of hand.

Suppose it were true; how would it be done? If it were fly by wire throttle, then easy simply don't let the throttle open as far. But with pre fly-by-wire models with a mechanical throttle, I cannot see how it could be done without compromising emission standards.

So I am inclined to disbelieve it, does anyone have any evidence either way?

[Gazza]

I believe it to be true.


I have noticed a drop in acceleration, reset and all back to normal

[BladeRunner919]

I agree. And the question of cable-throttle and fly-by-wire throttle is irrelevant - in both systems you press the accelerator and a throttle flap opens and the ecu fuels accordingly. In one the cable pulls the throttle open and in the other the flap is opened electronically - it's the same difference. Both have an ecu controlling fuelling and spark and so on.

[boustrophedon]

I agree. And the question of cable-throttle and fly-by-wire throttle is irrelevant - in both systems you press the accelerator and a throttle flap opens and the ecu fuels accordingly. In one the cable pulls the throttle open and in the other the flap is opened electronically - it's the same difference. Both have an ecu controlling fuelling and spark and so on.

Not quite the same, with fly-by-wire there is a computer between you and the throttle butterfly, the computer can open it as far or as little as it is programmed to, or as slow or fast. So it would be quite easy to program it to only permit say an 80% or 70% throttle opening when the red light is lit. The ECU would of course supply the correct spark and fuel for that throttle opening. Easy

With a mechanical linkage there is no scope for computer intervention between you and the throttle butterfly, 'tis fixed, and the ECU should be compelled by the stoichiometry of the combustion process to provide the correct fuel and spark timing. It could retard the spark, but that might have illegal knock ons for exhaust emissions. So much easier with Fly-by-wire.

[BladeRunner919]

I agree. And the question of cable-throttle and fly-by-wire throttle is irrelevant - in both systems you press the accelerator and a throttle flap opens and the ecu fuels accordingly. In one the cable pulls the throttle open and in the other the flap is opened electronically - it's the same difference. Both have an ecu controlling fuelling and spark and so on.

Not quite the same, with fly-by-wire there is a computer between you and the throttle butterfly, the computer can open it as far or as little as it is programmed to, or as slow or fast. So it would be quite easy to program it to only permit say an 80% or 70% throttle opening when the red light is lit. The ECU would of course supply the correct spark and fuel for that throttle opening. Easy

With a mechanical linkage there is no scope for computer intervention between you and the throttle butterfly, 'tis fixed, and the ECU should be compelled by the stoichiometry of the combustion process to provide the correct fuel and spark timing. It could retard the spark, but that might have illegal knock ons for exhaust emissions. So much easier with Fly-by-wire.

I wasn't really thinking in terms of the throttle opening more slowly - I was erring towards the fuelling being altered, but I guess the throttle response would be a way of doing it.

[lightning]

On my 3.0 the idle had all of a sudden become slightly imperfect and on a light throttle there was just a hint of hesitation/misfiring.

After doing a full service (including spark plugs etc) it was no different. I then reset the service lights, and after that it was perfect!

I am thinking maybe it's to make you take it in for a service. As in "The yellow/red service lights are on and it's not running quite right"

[peter2b]

When my lights were reset at the shepshed meet I did notice after 30 or so miles that she was a bit more responsive (car that is)
Peter2b

[stevov]

By wire or cable is irrelevant. In the same way the ecu controls timing and fueling for various grades of fuel so the ecu will control fuel and timing when the system says something is not quite right. Not so much a limp home mode, but pull back a couple degrees timing and add a little fuel and presto slight power loss.

[littlefeller]

my fuel consumption improved after reset, i know this to be true as i always reset my mileage when i fill up, it degrades very slowly and with the fluctuations in fuel price you dont really notice it, its only after the rest set it becomes apparent. cant say i noticed any performance improvement though, then again i didn't put the car on a dyno either (can anyone really notice a few extra ponies through the seat of there pants, some believe they can )