Hesitation off idle

[e12mat]

Gents,

Once again I am in need of your wisdom.

After an extensive program of replacement the cerb has been running absolutely spot on except for a slight issue.

The car idles fine and accelerates cleanly if given a fair amount of throttle, however if you just come of the idle stop with the throttle the car bogs down.

I will be getting in there with the laptop and software shortly, but my thoughts were that it could be fuelling related i.e. over fuelling because it's bogging down.

I presume this could be lambda or adaptives related, problem is worse when cold almost to the point of stalling but is still there when warm. I thought it could be water in the lambda connections but surely after a good warm and drive these would be dried out?

Thanks for your help.

[gruffalo]

First thing I would check would be the lambda sensors as you mention, sounds like one is playing up.

[ridds]

Yep lambda sensors and throttle pots.

[e12mat]

Hi Guys

I've attached the adaptives and the both lambda sensors are operating fine and pretty much just after start up as they should. I was able to replicate the issue and you can see the massive adaptive reduction to both banks at 1000 rpm at throttle point 2 so this is what’s causing the stalling.

I think best course of action is to reset adaptives and start from there. Is this best done warm or hot? Last time and had to use the throttle to keep the car from stalling I presume this is ok?

Thanks for the help.

[spitfire4v8]

you have to use throttle to stop it stalling because the site at closed throttle just down from idle (750rpm) is too weak for your car, it's adding 30+% to get back to lambda=1 which is already a weak mixture anyway. You have some massive lambda swings around idle. are you sure your car is set up properly / valve clearances / cam timing etc etc?
It's also interesting to see you've managed to get the ecu to learn values at 250rpm! and at throttle 11 (lambda control is disabled over throttle 10) .. needs more looking at.
I don't normally recommend resetting the adaptives if you don't have to .. you undo all the good learning work the ecu has done for no good reason unless you've corrected something and are deleting bad values. However in your case I'd say zero them all and start over again and see what happens.

Edited by spitfire4v8 on Sunday 12th August 18:12

[e12mat]

Upon closer inspection I think that the idle was set too low at the throttles which the ECU over compensated for with a mass over fuelling. In the transition between 750rpm to 1000rpm the ECU is then trying to reduce the massive over fuelling that occurred previously.

I’m not happy with the throttle setup at the minute and I’m going to fit an idle adjustment on the offside throttle which will completely eliminate any slop, as the throttles are balanced at idle and go right out when the accelerator is first pressed by probably 4 %.

[spitfire4v8]

interesting you should say that .. looking at your tables i was surprised just how in-sync the adaptions are through the rev range! moving the throttle stop is defo a good move though anyway