Stalling at idle but only after dab of throttle

[MidLifeCrisis]

I know the 'stalling at idle' question has been done to death but .....

.... I have a situation where, once engine is warmed up so its off the choke, the engine will stall at idle;
But, here is the odd thing; if I restart without touching the throttle it will idle nicely but as soon as I touch the throttle, then let the revs die down again it stalls; start up with no throttle and it's nice again, dab the throttle and the engine revs (as you'd expect) then as the revs die away again it stalls;
Anyone got any ideas??
What would be the difference in the carb state (assuming it's carb related) between a start with no throttle, and the state after the throttle has been slightly opened, then closed again (ie a dab of throttle)??

(This situation just happened again while I was out just now and eventually, after me sitting in a carpark playing around with different starting, throttle ideas, it self-healed and ran just fine all the way home - so it's an intermittent problem (which doesn't make it any easier to solve)?!?)

Ideas?
Tests?

[itchyfeet]

Could just be a sticky throttle thats set a bit too low on the throttle stop screw.

try starting then in engine bay push throttle home to the stop ( not open)

I suppose air leak may also do it, lean on revs falling more likely to stall than lean on steady idle.

[MidLifeCrisis]

Thanks - interesting thoughts.
I would have assumed it was a vacuum leak somewhere but it seems to be intermittent and varies on that throttle blip which would suggest that it's something else - although I like your idea that decaying revs are more likely to 'stall' than steady revs ....... don't understand it ..... but like the idea!!

[Smosh]

I would check the throttle stop screw also, but it could also be an idle mixture... I only say that because I fixed a similar problem on an old mini that way. If I just gave the mini a gentle quick rev at idle as it settled to idle it would drop just below tick over speed, however, if cold it used to drop a bit too low before settling and stall or almost stall!

dunno if that made sense? Anyway, give the card a bit of a clean and the van decent blast. Might sort it out!

[itchyfeet]

Timing is also on the move when you blip the throttle, the vacuum advance is reduced if it's working.
do you know what your idle revs are?

[MidLifeCrisis]

Timing is also on the move when you blip the throttle, the vacuum advance is reduced if it's working.
do you know what your idle revs are?

Nope - don't have a rev counter unfortunately
But when I blip the throttle (which makes it stall) I'm giving it the lightest touch so can't imagine that timing would move much if at all???

Anyway, give the card a bit of a clean and the van decent blast. Might sort it out!

The rest of your post made sense - but I don't understand this bit - did your spellcheck go crazy?!?!

[Smosh]

Haha! I was meant to say give the carb a clean and take the van for a blast. I.e. drive the van and once warm Sit at mid to high revs for a few minutes, accelerate hard up through the gears. I'm not convinced where that actually helps, but living on a small island the van is always better after a nice run in the UK!

If you have a fancy multimeter you can do it in the from the engine bay. Someone else will have to explain that though, I can never remember which wire to connect to!

[MidLifeCrisis]

Anyway, give the card a bit of a clean and the van decent blast. Might sort it out!

Well, I gave the card a bit of a clean and the van decent blast and it all seems to be ok at the moment - possibly just a bit of dirt/debris in the idle systems but only time will tell!! I'm holding my breath - thanks for the ideas/advice everyone (however cryptic!!)

[kevtherev]

It read like a blocked idle jet to me too.
A partially functioning anti dieseling valve will have the same effect

[MidLifeCrisis]

It read like a blocked idle jet to me too.
A partially functioning anti dieseling valve will have the same effect

Yeah - I thought I'd got it sussed at one point when I discovered that the wiring to the anti-dieseling valve was pretty dodgy (old partially broken wiring) but I repaired that and the problem didn't seem to go away ....

[kevtherev]

It read like a blocked idle jet to me too.
A partially functioning anti dieseling valve will have the same effect l

Yeah - I thought I'd got it sussed at one point when I discovered that the wiring to the anti-dieseling valve was pretty dodgy (old partially broken wiring) but I repaired that and the problem didn't seem to go away ....

ok at least you eliminated it

[MidLifeCrisis]

It read like a blocked idle jet to me too.
A partially functioning anti dieseling valve will have the same effect l

Yeah - I thought I'd got it sussed at one point when I discovered that the wiring to the anti-dieseling valve was pretty dodgy (old partially broken wiring) but I repaired that and the problem didn't seem to go away ....

ok at least you eliminated it

Well - I eliminated the last several inches where it separates out to feed the coolant temp switch and then the idle-cutoff solenoid - I suppose it could be dodgy in the single wire that runs from there into the black box of tricks - but that seems healthier (it's in a plastic ducting for a start!!

Have a feeling this one will return in the future!! Fingers crossed (that it won't)

[Smosh]

Anyway, give the card a bit of a clean and the van decent blast. Might sort it out!

Well, I gave the card a bit of a clean and the van decent blast and it all seems to be ok at the moment - possibly just a bit of dirt/debris in the idle systems but only time will tell!! I'm holding my breath - thanks for the ideas/advice everyone (however cryptic!!)

You saying my advice wasn't clear and concise? Haha! Pleased it is sorted, may be worth scheduling in a proper carb clean down the line!