Cutting out "sometimes" when slowing down

[gmw9666]

Right then collective brains

Many of you know my car, Chedders old motor, so its not standard in any way (thought I'd cover that off first before to prime everyone's grey matter)

The last 2 times I've taken her out, as I'm heading back from a good run, and hitting a more urban town area.......traffic lights, round about's etc she cuts out / stalls when I'm slowing down and changing down gear as I come to a halt.

She will start again with plenty of throttle or I have used my heel / toe skills to keep the revs up and slow at the same time but clearly cant do that forever

I've checked all the hoses with carb cleaner so I think I can rule out and air leak

This only happens when she is up to temperature, does not happen at all from cold

Thoughts and suggestions all

[mrzigazaga]

Hi Mate...This is probably not related but when i had my 280i supercharged mine was cutting out every time the revs dropped below 900rpm...Especially when changing down approaching lights or roundabouts and my issue was fuelling..It was set up soon after on a Rolling Road and everything was fine...Ziga

[gmw9666]

mrzigazaga said:

Hi Mate...This is probably not related but when i had my 280i supercharged mine was cutting out every time the revs dropped below 900rpm...Especially when changing down approaching lights or roundabouts and my issue was fuelling..It was set up soon after on a Rolling Road and everything was fine...Ziga

Fuelling, interesting......was yours running rich out of interest as mine smells very rich indeed

She's going in for a full service next week then RR after for a tune so if that's the case, easy fix case closed lol

(have been recommended these guys for the RR / remap on the Emerald, any others suggestions for the midlands? = http://www.kitsandclassics.co.uk/ )

[mrzigazaga]

gmw9666 said:

Fuelling, interesting......was yours running rich out of interest as mine smells very rich indeed

It was running rich...It had to be leaned off a fair bit as the FPR i had made would provide more fuel when adding boost...Can you not ask Tony what it should be as if it is this then surely he would of come across it at some point in the beginning....Cheers...Ziga

[gmw9666]

mrzigazaga said:

It was running rich...It had to be leaned off a fair bit as the FPR i had made would provide more fuel when adding boost...Can you not ask Tony what it should be as if it is this then surely he would of come across it at some point in the beginning....Cheers...Ziga

He mentioned it would need a re map when I bought and the car has really not been used for a few years so time does take its toll when they are not used

I just want to cross off any obvious items before the re map

[keatsie]

Sounds like the base idle is not set correctly, or that the idle stepper motor is sticking and stalls before it gets a chance to catchup. Check the throttle pot is correct at closed throttle as well.

[V8 Fettler]

Is this flapper or hotwire?

[gmw9666]

V8 Fettler said:

Is this flapper or hotwire?

[V8 Fettler]

This doesn't look like a flapper!

[keatsie]

Supercharger mmmmmmmmmm,

[chedder]

Hi Glen, surprised that it's running rich as it has always been very low on polutants since the Emerald was fitted, poss the coolant sensor needs recalibrating on the
Emerald map, just a quick thought, if its cutting out on overun, what does the fuel pressure gauge do when it happens? if it's dipping then you should be able to alter the Vortec fuel pressure regulator as it has adjustment for vacuum.

Chedder

[gmw9666]

chedder said:

Hi Glen, surprised that it's running rich as it has always been very low on polutants since the Emerald was fitted, poss the coolant sensor needs recalibrating on the
Emerald map, just a quick thought, if its cutting out on overun, what does the fuel pressure gauge do when it happens? if it's dipping then you should be able to alter the Vortec fuel pressure regulator as it has adjustment for vacuum.

Chedder

Top tip tony, not been viewing the fuel pressure gauge as I'm generally trying not to stall lol

Will see if I can multi task and do both on the next run

Was out in her today scaring the locals, she's such a beast, love it

[chedder]

[quote=gmw9666

Was out in her today scaring the locals, she's such a beast, love it
[/quote]
Excellent!

Hi Glen, the Vortec unit should be running at about 45psi on static idle and drop to about 43psi when running if all ok then the next thing to check is the Air Idle Control valve (just behind the alternator and above the offside rocker cover (BMW item) This is controlled on the Emerald map and is programmed with various correction factors, coolant temp and throttle pot position etc. if the problem is only occuring at higher water temps then adjustment is straight forward on the correction tables.
Could be that the AIC is sticking when warm, maybe disconnect it from the pipes and give it a squirt of carb cleaner to free it up?

Chedder

[gmw9666]

Does this AIC look stuck almost closed to you

[chedder]

Cant be sure if it is or not, it is basically a stepper motor and as such has a base idle setting for cold running and should adjust with the map when the water temp and throttle position change, but I would be inclined to check the Vortec FPR settings first as this is the only item on the fueling that is not controlled by the ECU.

Chedder

[gmw9666]

chedder said:

Cant be sure if it is or not, it is basically a stepper motor and as such has a base idle setting for cold running and should adjust with the map when the water temp and throttle position change, but I would be inclined to check the Vortec FPR settings first as this is the only item on the fueling that is not controlled by the ECU.

Chedder

Interesting development, quick squirt of carb cleaner and the AIC started to flap. The "door" now have movement in it and flaps like its on a spring. Could be it was stuck and not adjusting when warm.

Will check tomorrow to see how she goes and also check the fuel pressure whilst I'm at it

Ta for the input, always tricky when working on a car someone else built :-)

[adam quantrill]

Well I was going to suggest the dreaded Coolant Temperature Sensor but it seems this probably doesn't exist any more on this car... ;^)

[gmw9666]

Well I found some instructions (I love google), its not just a fuel pressure regulator but a Super Fuel Management Unit, how cool does that sound

Will have a play later to ensure the static idle pressure is about 45 as you suggested Tony

http://www.vortechsuperchargers.com/images/71.pdf

[chedder]

gmw9666 said:

chedder said:

Cant be sure if it is or not, it is basically a stepper motor and as such has a base idle setting for cold running and should adjust with the map when the water temp and throttle position change, but I would be inclined to check the Vortec FPR settings first as this is the only item on the fueling that is not controlled by the ECU.

Chedder

Interesting development, quick squirt of carb cleaner and the AIC started to flap. The "door" now have movement in it and flaps like its on a spring. Could be it was stuck and not adjusting when warm.

Will check tomorrow to see how she goes and also check the fuel pressure whilst I'm at it

Ta for the input, always tricky when working on a car someone else built :-)

Hopefully thats sorted it!
Chedder

[gmw9666]

ok sit. rep.

Cleaned the AIC = check

Checked the fuel pressure at idle / 43 ish PSI = check

Tried adjusting the vacuum screw on the FMU, it was slack and almost out so wound it in a = no changes to fuel pressure at all regardless of vacuum screw position

Took for a drive to see whats what now she was warm.............thought initially she was fine..........trying to provoke it to stall........i.e. speed up and slow down rapidly dropping the clutch..........all fine so far

So turned for home with a big smile as I approached a mini round about.......then grrrrr.........she cuts out

I coasted to a stop, pressed the start button, she started reluctantly so nursed her home, interestingly she didn't cut out again

Been thinking.......fuel filter?......she has been sat a bit so could have some crud impacting flow?

Any other thoughts are most welcome

nb - throughout the journey the fuel pressure stayed flat, didn't move the 43 ish PSI