Technical Idle speed questions?

[dac69er]

The idle speed on my sporting seems to take a while to drop to normal idle speed. Around 5-10 seconds ish.

I have tried resetting the ecu etc etc and not got very far. I monitored the idle stepper motor position on lAW scan and it changes, but just seems to take a while to do it.

Any ideas???
Do the stepper motors get slow or Do they usually just fail.
I'm sure before the engine swap it was far quicker than it is now.

 

[dac69er]

Had a spare 15 mins this morning so swapped out the idle stepper motor. It made no difference.

It's like the revs hang for a bit and it take a few seconds to drop back down to idle.

Once warmed up it's about 1200 rpm then it takes around 10 seconds (sometimes a bit quicker) to drop to about 850ish rpm.

When cold all these figures are a bit higher due to the engine being cold, but it reacts in the same way.

I am sure it never used to be like that, but maybe it was and it's normal!? When I took it for MOT a few months back the tester mentioned it seemed to idle high initially.

Any other ideas?

 

[jm1489]

I have had loads of seic and own four at the moment, bottle top and a packet of fags is enough to buy one, don't remember any of them being happy at idle... certainly not the present collection, cleaned throttle bodies, ecu resets etc, new crank sensors etc.. etc.. I don't think they do sit into a gentle low idle from the factory? The last one I sold was in August, the chap did a 300 mile round trip after collection and text me to say that the car was running like a dream after the trip! The idle was high and it used to hunt before then, maybe the little engine needs more than Town use?

 

[dac69er]

It idles fine (for an spi engine). It's just the speed at which the rpms drop to idle that doesn't seem right to me.

The engine is a complete fresh rebuild so it's all clean and put together properly etc. All sensors have been checked and are functioning perfectly ok.

As I said, they may all be like that, but I just can't remember it hanging so much before settling to it's normal idle speed.
Maybe it has an air/vacuum leak, but I would have though the idle would always be high if that was the case?

 

[jm1489]

Could be snagging on throttle, cable or worn return spring?

 

[dac69er]

Not that. Throttle returns to the same position every time.
It's a sparky throttle body and is in spot on condition.

When you open the throttle the stepper motor moves to a more open position. It just seems to take too long to decide to close enough to control the idle.

As I said, it always get there, just takes up to 10 seconds ish, which seems too long!?

I will try and get a video of what I mean.....

 

[jm1489]

Had similar issue with an Audi A4, that time it was a worn throttle body but no help if your set up is good and XR3 which was a holed diagram in the manual injector pump. Injectors? If the shut off thingy is closing too slowly it could be a signal problem? Scrap the lot and put a bank of Kawasaki carbs on!

 

[dac69er]

All sensors check out fine.

It has taken me 3 years to set up a single carb on my bike. I'm sure it will be far more hassle than it's worth sticking 4 carbs on a car that's originally injection!

I was hoping someone with an spi engine would feedback how their car drops to idle as it might just be normal and I'm worrying about nothing!?

 

[dac69er]

not the best video. but gives you an idea.

when i rev it, the revs hang for a bit just above 1000rpm and then slwoly drop to normal idle speed? this is probably the best it gets, it normally hangs for longer before dropping down to normal.

 

[dac69er]

issue is now sorted.

i adjusted the throttle stop position to close the butterfly slightly more.


it now drops down to idle perfectly